General Chemistry 1 Lab Manual_Student_10_24_22

II Beer’s Law Safety ______________________________________________________________ 54 Beer’s Law Exper imental Procedures ___________________________________________ 55 Beer’s Law Data Sheet _____________________________________________________ 58 Beer’s Law Report Requirements __________________________________________ 59 Beer’s Law Report Rubric ______________________________________________ 60 Beer’s L aw Calculations _____________________________________________ 63 Experiment 5: Determining the Enthalpy of a Chemical Reaction ____________ 64 Determining Enthalpy Introduction __________________________________________ 65 Determining Enthalpy Safety ____________________________________________________ 72 Determining Enthalpy Experimental Procedures __________________________________ 73 Determining Enthalpy Data Sheet ____________________________________________ 79 Determining Enthalpy Report Requirements _________________________________ 86 Determining Enthalpy Report Rubric _____________________________________ 87 Determining Enthalpy Calculations ____________________________________ 89 Experiment 6: Cycle of Copper ________________________________________ 93 Cycle of Copper Introduction _______________________________________________ 94 Cycle of Copper Safety _________________________________________________________ 97 Cycle of Copper Experimental Procedures _______________________________________ 98 Cycle of Copper Data Sheet ________________________________________________ 102 Cycle of Copper Report Requirements _____________________________________ 104 Cycle of Copper Report Rubric _________________________________________ 105 Experiment 7: Chemical Bonding _____________________________________ 108 Chemical Bonding Introduction ____________________________________________ 109 Chemical Bonding Experimental Procedures ____________________________________ 111 Chemical Bonding Data Sheet ______________________________________________ 113 Chemical Bonding Report Requirements ___________________________________ 115

V provide a thorough explanation (e.g., http://plagiarism.org/plagiarism-101/types-of- plagiarism/ ). 1. Cut and paste from another student's report The original report may belong to a student in another class, a student who took General Chemistry in a previous semester, or maybe the student is your lab partner. It doesn't matter; you cannot do this for any reason. This is plagiarism. Suppose you don't have time to write your report, turn it in late for partial credit. If you have trouble writing clearly, get help from the Academic Support Center, your lab instructor, or a tutor. There is no excuse for copying another student's lab report. 2. Reuse the lab report that you wrote when you took this class previously Reusing a report that you wrote previously is just like copying another report, except that you were the original report's author. It doesn't matter. This is plagiarism. Since this is a new semester, we expect your work to be new as well. Your reports should be your own original work, not copies of work you did last semester. 3. Copy text from another source Another source of text could be a website or the lab handout itself. Copying text from another source is wrong, just like copying another student's lab report is wrong. Students sometimes copy the procedure directly from the lab handout. They have explained that since they followed the procedure exactly as written in the handout, they should write their procedure precisely as provided. No. This is plagiarism. 4. Quote extensive amounts of text Do not copy and paste sentences into your report, then put quotes around them. Quoting another source in a lab report shows that the student does this because they know the quote contains the correct information, but the student is either too lazy or does not understand what the quote means. This is plagiarism. Here is an example with the copied and quoted text highlighted: Lightning is a spectacular event. Lightning bolts are described as "a common phenomenon — about 100 strike Earth's surface every single second — yet their power is

VIII How to Keep a Hand-written Lab Notebook The expectations of a lab notebook are that any novice researcher can refer to this document and perform the experiment exactly the way the writer of the notebook had done. The results from the lab notebook should be reproducible and easy to follow. These are not meant to be publishable documents; therefore, they do not need to be perfect. The most important details about a lab notebook are that every detail of the experiment must be recorded in the book. If the researcher had to change the procedure in any way, those changes must be documented for the next person to reproduce. All data found must be recorded in it. Calculations or explanations to comprehend the results must be documented as well. Below is an example of a lab notebook. Every lab notebook should include the following: 1. Table of Contents 2. Numbered pages 3. Journal entries for each lab performed; Must include the following information: a. Lab Title b. Date Lab was performed c. Objectives of the lab d. Condensed Procedure e. Data tables that reflect the data sheet: Must include graphs f. Calculations and Conclusions g. Discussion questions Example Notebook:

XI 2. Start by creating a new project: 3. Next, select Project and fill in the criteria with your information: 4. The location will be your name. You can then create an entry by clicking the + sign on the left side of the page, select entry, then blank entry:

XIV Lab Notebook Rubrics Every student will be required to keep an electronic notebook online through Benchling. The data in this notebook will be accessible by the student, their respective GSA, the Lead GSA, and the course instructor for grading. The lab notebook is primarily for the student to track their data and results throughout the Lab. Lab notebooks grades principally depend on COMPLETION. IF the student feels this is unfair or has any further questions, please contact your GSA or course instructor. Pre-lab notebooks are due at 11:59 pm the day before the Lab meets to perform the experiment. Post-Lab notebooks are due at 11:59 pm a week after the Lab performs the experiment. Pre-Lab Notebook Objectives Procedures Discussion Questions 5 pts: A brief explanation of what the student will learn from this Lab. What question will this experiment answer? 5 pts: Full credit requires condensed procedures from the lab manual written in your own words. 5 pts: Discussion questions pulled directly from the lab manual. Plagiarized questions are to ensure students have seen the questions. 2.5 pts: The student tried, but the objective does not hit the mark. 2.5 pts: Procedures not complete or cannot be followed. 2.5 pts: Some questions included but not all. 0 pts: None included, not completed on time, or plagiarized. 0 pts: None included, not completed on time, or plagiarized. 0 pts: None included, not completed on time, or plagiarized.

XIII 7. It should include the discussion questions for each experiment. The answers are required but do not add the actual discussion questions. Answer all parts of the questions in complete sentences and paragraph form. NO bulleting or numbering is acceptable. Formatting expected in your report: a. The header should be on the top left corner of the first page of the report. b. All tables must be labeled ABOVE the table. Under each table, provide a one- sentence description of what the table is showing the reader. c. Any figure or graph must be labeled UNDER the figure or graph. Following the figure/graph label, provide a one-sentence description of what it is showing the reader. d. Analysis should be a separately labeled section. e. You must use either 12-point Times New Roman font or 11-point Arial font. f. You must double-space. g. The text of the report must be justified. h. Standard 1-inch margins. i. Must be writing in the third person (i.e., no I, you, we, etc.) and past tense. j. Everything must be typed in complete sentences and paragraph form. Bulleting or numbering is NOT ACCEPTABLE. Failure to adhere to any of the above guidelines will result in points deducted from the assignment. Failure to turn the assignment in on-time will result in a 50% points reduction. If you have questions regarding these guidelines or Lab report expectations, contact your GSA or the Lead GSA.

XVI Lab Policies and Safety Violation Penalty Not wearing goggles when directed. 1) Warning. 2) Earn 50% off your lab notebook. 3) The student gets dismissed from Lab immediately and receives a zero on that day's assignments with no opportunity to make up the work. *For safety reasons, GSAs and course instructors may skip to third offense penalty at their discretion. Not wearing gloves when directed. Not wearing lab coat during experiments or unbuttoned lab coats. Not wearing long pants or a long skirt that completely cover your legs. Not wearing a face covering over both your nose and mouth. Not wearing shoes that completely cover your feet. Refusing to tie back long hair. Eating or drinking in the Lab. Including chewing gum! Food or drink at the student's lab workspace. Behaving inappropriately (at the discretion of any GSA or Florida Tech Staff member). Show up to Lab unprepared: forgot goggles, lab coat, appropriate shoes/attire, etc. Receive 50% off your lab notebook. You will have 5 mins after the start of the Lab to obtain your materials. Failure to obtain materials results in a zero for that day's assignments with no opportunity to make up the work. Failure to complete the pre-lab quiz AND pre-lab notebook before attending Lab. Dismissed from Lab and receive a zero on that day's assignments with no opportunity to make up the work. Have food or drink in the Lab away from your workspace but still in the lab room, including closed containers in your backpack. Receive 50% off your lab notebook. Arrive late within the 5-minute window. Receive 50% off your lab notebook. Arrive late after the 5-minute window. Dismissed from Lab and receive a zero on that day's assignments with no opportunity to make up the work.

17 Experiment 1: Determining the Density of Metals and Liquids Experiment 1: Determining Density

18 Determining Density Introduction Materials can be distinguished from one another because they have different physical and chemical properties. A property that is often used to identify materials is density. Density is defined as the amount of matter in a given space, which correlates to the ratio of a material’s mass to its volume. ????𝑖??? = ???? ?????? The mass is the amount of matter in a material or object, usually given in grams (g) or kilograms (kg). Whereas volume is the amount of space the object occupies usually given in terms of milliliters (mL), liters (L), or cubic centimeters (cm3). In this experiment, you will measure the mass and volume of six unknown metal samples. The metal samples may vary in mass, size, or shape. In Part 1 of this experiment, you will calculate the volume of the samples by measuring the length, width, height, and/or diameter of the object (depending on its shape) using a digital caliper. Table 1 provides volume equations for a selected group of shapes. Some of the metal objects are not perfect examples of any of the shapes. You must choose which shape they most closely resemble and use the corresponding formula for volume. Table 1: Volume Equations for 3D Shapes Shape Equation Shape Equation sphere V = 4/3 π r 3 pyramid V = (L x W x H) / 3 rectangular prism V = L x W x H prolate ellipsoid V = 4/3 π r 2 (L/2) right circular cylinder V = π r 2 H right circular cone V = π r 2 (H/3) NOTE: A straight line from the center measures the radius of a circle. A prolate ellipsoid is an elongated spheroid 3-dimensional shape. In Part 2, you will determine the volume of the samples by water volume displacement using a graduated cylinder. The data obtained in both parts will be used to calculate the densities of the unknown metal samples. From the density, you will identify the composition of the metal samples by comparing them to the theoretical densities of the metals presented in Table 2.

19 In Part 3, you will explore the power of density and determine the density of six solutions. You will create six separate solutions of increasing amounts of salt with a consistent amount of DI water. By increasing the amount of salt in the solution but keeping the amount of water constant, you prepare solutions that have increasing densities. The more salt that is mixed into a measured amount of water, the higher the density of the solution. The density straw shows a solution with a low density stacks on top of a solution with a higher density. You might expect the solutions to just fall out of the straw as you lift the straw from a solution. However, the invisible forces acting on the liquid inside the straw are manipulated by holding your finger to block the top opening of the straw. You create a pressure seal with your finger causing the external air pressure (the upward force) to become stronger than gravity (the downward force) acting on the liquid. As the capped straw is removed from the liquid gravity tugs the solutions downward, which creates a slight vacuum in the empty part of the straw. That lowers the air pressure inside the straw, which is why you need your thumb to cap the straw. This prevents air pressure from equalizing in the straw. If you remove your thumb, the air pressure equalizes, and gravity simply moves the colored solutions out. Table 2: Density of Selected Metals Metal Density (g/cm 3 ) Metal Density (g/cm 3 ) Mg 1.74 Brass 8.53 Al 2.70 Pb 11.34 Ti 4.51 Cu 8.96 Ag 10.5 Ni 8.90 Zn 7.14 Mn 7.3 Sn 7.26 Au 19.3 Steel 7.86 Zr 6.52

20 Determining Density Safety Always wear proper personal protective equipment (i.e., your goggles and lab coat). Always wear proper attire: long pants/skirt with no holes, shoes that completely cover your feet, and keep long hair tied back. Gloves must be worn while handling chemicals. However, gloves must not be worn in the hallways or when interacting with non-chemical entities (e.g., door handles, eyes, or laptops/cell phones). Remove gloves before exiting the lab unless transporting chemicals with the aid of an ungloved partner to open doors. Place your backpacks, skateboards, etc., on the counter in the back of the lab. It is important that peo ple don’t trip and fall when working around hazardous chemicals. You may not wear headphones in the lab because they distract you from your environment creating a hazardous lab space. Waste Disposal Dispose of all waste in the non-regulated waste container labeled NR. Disposable face masks can be thrown in the regular trash.

21 Determining Density Experimental Procedures Part 1: Determine Density by Mass and Dimensions 1. You were given a bag with 6 unknown metal samples. Record the Bag ID on your data sheet and in your lab notebook. 2. Identify the shape of each metal sample and list ALL physical properties of the sample on your data sheet (i.e., shiny, smooth, color, textur e, etc.). • Note – You will compare the density from Part 1 to Part 2. Be sure you can quickly identify metals 1-6 based on their physical properties. Record measurements for the same metal in both tables on the Data Sheet and in your lab notebook (i.e., data for Metal 1 in Table 1 should be the same as the data for Metal 1 in Table 2). 3. Weigh each metal and record the mass on your data sheet and in your lab notebook. Significant figures are essential. 4. Take the necessary measurements of length, width, height, and diameter (depending on the shape) using the digital caliper. Record the measurements in your lab notebook. Significant figures are essential. 5. Calculate the volume of each metal sample (reference Table 1 in the procedure). Record the volume in your lab notebook. NOTE: Not all boxes on the lab notebook will have a value. (e.g., A rectangular prism does NOT have a diameter). Significant figures are essential. 6. Calculate the density of each metal sample. Record the density in your lab notebook. Significant figures are essential. Part 2: Determine Density by Mass and Water Volume Displacement 1. Based on your volume measurements in Part 1 and the size of your metals, choose the appropriate graduated cylinder to measure the water-volume displacement of each metal (50 mL or 10 mL). Choosing the correct glassware will result in more accurate results. Your metal sample should fit into the chosen graduated cylinder EASILY. The metal should not get stuck inside the graduated cylinder. 2. For each sample, fill the graduated cylinder with enough tap water so that, once added, the metal sample will be completely submerged in the water without going higher than the upper-most increment. Record the exact volume of the water in the

22 graduated cylinder in your lab notebook. Significant figures are essential. • For example, if your volume for a given metal was 5.0 g/mL in Part 1, you may want to try adding 7 mL of tap water in your graduated cylinder to start. 3. Tilt the graduated cylinder as far as possible (without spilling any water) and VERY CAREFULLY SLIDE in the metal sample to the bottom of the graduated cylinder without breaking the glass or splashing any water out. Record the volume of the water with the metal in your lab notebook. Significant figures are essential. 4. Calculate and record the volume of each metal in your lab notebook. Significant figures are essential. 5. Calculate and record the density of each metal in your lab notebook. Significant figures are essential. Part 3: Liquid Layers – Salt Water Density Straw 1. Clean 5 test tubes and label them. 2. Measure 0.50 gram (g) of salt and place it into test tube one. 3. Repeat step 2, increasing the amount of salt by 0.50 grams for each test tube (i.e., 1.00 g for test tube #2, 1.50 g for test tube #3, etc.) 4. To each test tube, add 12 mL of warm DI water. 5. Stir each salt and water solution with your glass stir rod until all of the salt has been dissolved. 6. Use food coloring to dye the solutions in each test tube. Add 3-4 drops of red to test tube #1, 1 drop of red and 2 drops of yellow to test tube #2, 3 drops of yellow to test tube #3, 0.5-1 drop of green to test tube #4, 0.5-1 drop of blue to test tube #5. 7. Obtain a clear drinking straw. Keeping both ends open, dunk the bottom end of the straw about 0.5 inches into the liquid of test tube #1. Cap the top of the straw firmly with your thumb and remove the straw from the solution. 8. Now that you have the first solution in the straw, dip the end of the straw into test tube #2. This time dip the straw about 0.5 inches deeper than you did into the first solution. After you’ve dipped the straw, lift your thumb and replace it. 9. Continue the dipping process until you have all six colored solutions inside the straw. It’s a density column of saltwater! 10. Dispose of all waste in the waste container labeled non-regulated (NR) waste.

23 Determining Density Data Sheet Name_______________________________________________________________ Section___________________ Date_____________________ Metal List ALL Physical Properties Mass (g) Length (cm) Width (cm) Height (cm) Diameter (cm) Volume of Object (cm 3 ) Density (g/cm 3 ) 1 Shape:_______________ 2 Shape:_______________ 3 Shape:_______________ 4 Shape:_______________ 5 Shape:_______________ 6 Shape:_______________

24 Identify each of your Metal samples: Metal 1: ______________________ Metal 2: ______________________ Metal 3: ______________________ Metal 4: ______________________ Metal 5: ______________________ Metal 6: ______________________ Metal Mass (g) (from Table 1) Did you use a 50.0 or 10.0 mL graduate cylinder? Volume of water (mL) Volume of water + metal (mL) Volume of metal (mL) Density (g/mL) Density (g/cm 3 ) From Table 1 1 2 3 4 5 6

25 Test Tube Salt (g) DI (mL) Density (g/mL) 1 2 3 4 5

26 Determining Density Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or rephrase what somebody else writes. Type the report using justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements Be sure you have shown ALL calculations on your lab notebook to receive full credit. Use Table 2 of the procedure and your calculated densities to identify the composition of your six metal samples. Record your results on the lab notebook. Discussion Questions Copy these questions into the lab notebook for perusal during the lab. Answer these questions in prose (complete sentences, paragraph form) in the lab report. 1. Which method of measurement would be more accurate to calculate the density of an object? Caliper/balance or volume based on the displacement of water? Why? What about irregularly shaped objects? (5 pts) 2. What is the definition of an alloy? Which metal(s) measured is (are) an alloy metal material. (HINT refer to Table 2 for possible alloys) (5 pts) 3. Sam needs 20 g of hydrochloric acid (HCl). The density of hydrochloric acid is 1.164 g/mL. Find the volume of hydrochloric acid they need. (5 pts) 4. A metal bar has a density of 15.9 g/mL what is the density in kg/L? (Show work for full credit) (5 pts)

27 Determining Density Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double-spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all.

28 Data & Results 7 points Types up all of the tables and data collected in the Lab. Includes figures. Tables are appropriately labeled (each correctly identified, appropriate title, and units are included), and data is complete. Required figures are also included. Data doesn’t match the Lab notebook; tables are presented incorrectly or not properly labeled, data makes no sense, etc. A picture or image of the data sheet or notes taken is given as data results (i.e., screenshots of the Benchling lab notebook). You are missing most or all data and results. Calculations 5 points This section includes typed examples of all designated calculations. Includes a typed example of all calculations performed. Units are included. Some calculations are missing, OR units are missing. A picture or image of the data sheet or notes taken is given as calculations OR none included. Analysis 8 points Brief but thorough explanation of results, trends, and what they mean. Includes a separately labeled section with an explanation of results, trends, and what they mean. Some trends are explained or missing or inadequate explanation. No analysis included. The student writes procedure as analysis. Discussion Question 1 5 points Which method of measurement would be more accurate to calculate the density of an object? Caliper/balance or volume based on the displacement of water? Why? What about irregularly shaped objects? Explains which method is better and why. Explains the correct methods for the shapes but does not explain why. No answer included, or answer does not make sense.

29 Discussion Question 2 5 points What is the definition of an alloy? Which metal(s) measured is (are) an alloy metal material. Gives the definition of an alloy and states which metals were alloys. Does not state definition of an alloy but states what metals were alloys. OR states definition of an alloy but does not state which metals were alloys. No answer included, or answer does not make sense. Discussion Question 3 5 points Sam needs 20 g of hydrochloric acid (HCl). The density of hydrochloric acid is 1.164 g/mL. Find the volume of hydrochloric acid they need. Shows complete calculation. States answer but does not show work. No answer included, or answer does not make sense. Discussion Question 4 5 points A metal bar has a density of 15.9g/mL what is the density in kg/L? Shows complete calculation. States answer but does not show work. No answer included, or answer does not make sense.

30 Experiment 2: Alka Seltzer Stoichiometry Experiment 2: Alka Seltzer Stoichiometry

31 Alka Seltzer Stoichiometry Introduction Stoichiometric measurements are among the most important in chemistry, they indicate the proportions by mass in which various substances react. Stoichiometry includes writing and balancing chemical equations, stoichiometric coefficients, molar ratios of reactants and products, limiting reagents, theoretical yields and percent yields. Alka-Seltzer is an over the counter antacid and pain relief medication which is taken by dissolving it in water before ingesting. This drug contains aspirin (acetylsalicylic acid), citric acid, and sodium bicarbonate (NaHCO 3 ). Immediately after the tablet is placed in water, an acid-base reaction involving sodium bicarbonate takes place which leads to the generation of carbon dioxide through bubbling. HCO 3 - (aq) + H + (aq) → H 2 O (l) + CO 2 (g) The release of carbon dioxide results in a net weight loss after the reaction. With the weight loss, one should be able to calculate the amount of sodium bicarbonate that reacted and determine the percent by mass of NaHCO 3 contained in Alka-Seltzer tablets.

32 Alka Seltzer Stoichiometry Safety Always wear proper personal protective equipment (i.e., your goggles and lab coat). Always wear proper attire: long pants/skirt with no holes, shoes that completely cover your feet, and keep long hair tied back. Gloves must be worn while handling chemicals. However, gloves must not be worn in the hallways or when interacting with non-chemical entities (e.g., door handles, eyes, or laptops/cell phones). Remove gloves before exiting the lab unless transporting chemicals with the aid of an ungloved partner to open doors. Place your backpacks, skateboards, etc. on the counter in the back of the lab. It is important tha t people don’t trip and fall when working around hazardous chemicals. You may not wear headphones in the lab because they distract you from your environment created a hazardous lab space. Waste Disposal Dispose of all waste in the non-regulated waste container labeled NR. Disposable face masks can be thrown in the regular trash.

33 Alka Seltzer Stoichiometry Experimental Procedures 1. Measure 60 mL of deionized water using a graduated cylinder. Pour into a 250 mL beaker. 2. In the balance room, weigh and record the total weight of the beaker and water using an electronic balance. 3. In the balance room, weigh and record the weight of an Alka-Seltzer tablet using a weigh boat. 4. After returning to the lab, drop the tablet into the beaker, carefully swirl the beaker to ensure complete dissolution of the tablet. 5. In the balance room, weigh and record the weight of the beaker and all the contents when the bubbling ceases. Refer to the data sheet and copy into your lab notebook. 6. After returning to the lab, wash and rinse the beaker with water. 7. Calculate the mass of the carbon dioxide generated. 8. Calculate the mass of NaHCO 3 reacted. 9. Calculate the percent by mass of the reacted NaHCO 3 in the tablet. 10. Repeat the experiment 5 times with the following vinegar and water amounts. a. 10 mL of vinegar + 50 mL of water b. 20 mL of vinegar + 40 mL of water c. 30 mL of vinegar + 30 mL of water d. 40 mL of vinegar + 20 mL of water e. 50 mL of vinegar + 10 mL of water respectively. Record values on the data sheet and in your lab notebook for each. 11. Plot the calculated percent by mass of the reacted NaHCO 3 in the tablet versus the volume of vinegar used using the Excel spreadsheet provided on Canvas. 12. Dispose of all waste in the waste container labeled Non-Regulated (NR) waste.

34 Alka Seltzer Stoichiometry Data Sheet Name_______________________________________________________________ Section___________________ Date_____________________ Experiment # Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Volume of vinegar (mL) 0 10 20 30 40 50 Volume of water (mL) 60 50 40 30 20 10 Weight of beaker and liquid (g) Weight of Alka- Seltzer tablet (g) Weight of beaker with liquid + weight of tablet (g) Weight of beaker with all contents after bubbling ceases (g) Weight loss (mass of CO 2 ) Mass of NaHCO 3 reacted % by mass of the NaHCO 3 in a tablet

35 Alka Seltzer Stoichiometry Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or rephrase what somebody else writes. Type the report using justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements Show one sample calculation for how you calculated the mass of NaHCO 3 from the amount of CO 2 released. Use Excel to plot the calculated percent by mass of the reacted NaHCO 3 in the tablet versus the volume of vinegar used. After the graph is complete, copy the graph into your lab report and lab notebook. Do not make graphs by hand, and do not put screenshots or pictures of your graph in your lab report. You must provide the graph and data table in your report to receive full credit. Discussion Questions Copy these questions into the lab notebook for perusal during the lab. Answer these questions in prose (complete sentences, paragraph form) in the lab report. 1. What is a limiting reactant? How does the graph change in correlation to the limiting reactant? Which would you identify as the limiting reactant in trial 2 of this experiment? Predict what might happen if the Alka-Seltzer tablet was dissolved in 60 mL of vinegar. How will this affect the graph? (10 pts.) 2. What will be the effect on the reaction if HCl is used instead of vinegar? How will the graph look? (5 pts.) 3. Balance the chemical equation below; (5 pts.) CO 3 2- (aq) + H + (aq) →CO 2 (g) + H 2 O (l)

36 Alka Seltzer Stoichiometry Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double-spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all. Data & Results 7 points Types up all of the tables and data collected in the Lab. Includes figures. Tables are appropriately labeled (each correctly identified, appropriate title, and units are included), and data is complete. Data doesn't match the Lab notebook. Tables are presented incorrectly or not adequately labeled. Data makes no sense, A picture or image of the data sheet or notes taken is given as data results (i.e., screenshots of the Benchling lab notebook). You are

37 Required figures are also included. etc. missing most or all data and results. Calculations 5 points This section includes typed examples of all designated calculations. Includes a typed example of all calculations performed. Units are included. Some calculations are missing, OR units are missing. A picture or image of the data sheet or notes taken is given as calculations OR none included. Analysis 8 points Brief but thorough explanation of results, trends, and what they mean. Includes a separately labeled section with an explanation of results, trends, and what they mean. Some trends are explained or missing or inadequate explanation. No analysis included. The student writes procedure as analysis. Discussion Question 1 10 points What is a limiting reactant? How does the graph change in correlation to the limiting reactant? Which would you identify as the limiting reactant in trial 2 of this experiment? Predict what might happen if the Alka-Seltzer tablet was dissolved in 60 mL of vinegar. How will this affect the graph? Defines limiting reagent. Calculates and determines the limiting reagent. Explains the effect on the graph. Only finishes one of the parts of the question. No answer included, or answer does not make sense. Discussion Question 2 5 points What will be the effect on the reaction if HCl is used instead of vinegar? How will the graph look? Explains both questions. Explains one question or the other but not both. No answer included, or answer does not make sense. Discussion Question 3 5 points Balance the chemical equation Gives the correct balanced equation. Not applicable the answer is either correct or wrong. No answer included, or answer does not make sense.

38 Alka Seltzer Stoichiometry Calculations The calculations performed in this lab can be as followed below. Please follow them as written, and if you have any further questions ask you GSA. According to the procedure, the data sheet asks you to solve for the mass of the reacted CO 2 from each tablet in the experiment after dissolving it with varying concentration of acid and water solutions. Therefore, the first calculation investigates the weight of the beaker with liquid + weight of the tablet: ??𝑖?ℎ? ?????? ?𝑖?ℎ ?𝑖??𝑖? + ??𝑖?ℎ? ?? ?????? ?𝑖?? 3 + 4 𝑖? ???? 𝑇???? = ??𝑖?ℎ? ?? ?????? ?𝑖?ℎ ?𝑖??𝑖? + ?????? ?𝑖?? 5 𝑖? ?ℎ? ???? 𝑇???? The data table (line 6) then asks for the weight of beaker after the solution content ceases bubbling. To do this, you must weigh the beaker after the experiment is complete, meaning no more bubbling of the solution occurs (line 6). From this measurement, you are then asked to find the weight loss (i.e. the mass of CO 2 ) from CO 2 gassing off: ???? ?? ?? 2 = ?𝑖?? 5 − ?𝑖?? 6 ?𝑖?? 7 𝑖? ???? 𝑇???? Lastly, you need to find the mass of NaHCO 3 reacted in the experiment (line 8). This can be done by: ???? ?? ?? 2 ????????? ????? ???? ?? ?? 2 ∗ ????? ???? ?? ??𝐻?? 3 1 ??? = ???? ?? ??𝐻?? 3 ??????? To accurately graph the percent by mass of the reacted NaHCO 3 (line 9), you must then convert the mass of NaHCO 3 reacted into a percentage like so: ???? ?? ??𝐻?? 3 ??????? ???? ?? ?ℎ? 𝐴?????????? 𝑇????? (?𝑖?? 4) ∗ 100 = % ?? ???? ?? ??????? ??𝐻?? 3

39 Experiment 3: Exploring the Properties of Gases Experiment 3: Properties of Gases

40 Properties of Gases Introduction Objectives During this experiment, you will: i. Conduct a set of experiments, each of which illustrates a gas law. ii. Gather data to identify the gas law described by each activity. iii. Complete the calculations necessary to evaluate the gas law in each activity. iv. From your results, derive a single mathematical relationship that relates pressure, volume, temperature, and number of molecules. The purpose of this investigation is to conduct a series of experiments, each of which illustrates a different gas law. You will be given a list of equipment and materials and some general guidelines to help you get started with each experiment. Four properties of gases will be investigated: pressure, volume, temperature, and number of molecules. By assembling the equipment, conducting the appropriate tests, and analyzing your data and observations, you will be able to describe the gas laws, both qualitatively and mathematically.

41 Properties of Gases Safety Always wear proper personal protective equipment (i.e., your goggles and lab coat). Always wear proper attire: long pants/skirt with no holes, shoes that completely cover your feet, and keep long hair tied back. Gloves must be worn while handling chemicals. However, gloves must not be worn in the hallways or when interacting with non-chemical entities (e.g., door handles, eyes, or laptops/cell phones). Remove gloves before exiting the lab unless transporting chemicals with the aid of an ungloved partner to open doors. Place your backpacks, skateboards, etc. on the counter in the back of the lab. It is important that people don’t trip and fall when working around hazardous chemicals. You may not wear headphones in the lab because they distract you from your environment created a hazardous lab space. Waste Disposal All waste is water which can be poured down the drain. Disposable face masks can be thrown in the regular trash.

42 Properties of Gases Experimental Procedures Part I. Pressure and Volume In this experiment, you will study the relationship between the volume of gas and the pressure it exerts while keeping the amount of gas and temperature constant. 1. Assemble the LabQuest by plugging it in and connecting the Gas Pressure Sensor to Channel 1 of the interface. Turn it on by pressing the start button. 2. Take a 20 mL syringe and position the front edge of the piston at the 15 mL mark. This will be the volume of air trapped in the barrel of the syringe for the first run. 3. Attach the syringe to the valve of the Gas Pressure Sensor, as shown in Figure 1. A gentle half turn should connect the syringe to the sensor securely. Important: Read the volume at the front edge of the inside black ring on the piston of the syringe, as indicated by the arrow in Figure 1. Figure 1: Gas Pressure Sensor Experimental Setup 4. Setup the data collection system to Time-Based mode . Data points or values should be recorded after 60 seconds, once the system equilibrates. Once ready, press the play button and record your observations. Save this as run 1. 5. While the syringe remains connected to the sensor securely, push on the piston of the syringe to decrease the volume of air trapped inside the syringe by 2 mL (at 13 mL). Hold the piston in place and record the pressure of the air in the syringe at this volume in your lab notebook. 6. Repeat step 5 three more times, pushing the piston in by 2 mL each time. Record the pressure at 11, 9, and 7 mL in the lab notebook. 7. Plot and graph the points in the spreadsheet provided in Canvas. Part II. Pressure and Absolute Temperature In this experiment, you will study the relationship between the absolute temperature of a gas sample and the pressure it exerts while keeping the volume and amount of gas constant.

43 1. Connect the Temperature probe to channel 2 of the interface of the LabQuest and discard the values from Part 1. Make sure the values from Part 1 are already in your lab notebook. 2. Assemble the apparatus shown in Figure 2 using a 600 mL beaker and a 125 mL Erlenmeyer flask. Be sure all fittings are airtight by screwing the plastic tubing and the Luer-lock valve to the rubber stopper. Twist the valve to the closed position . Make sure the rubber stopper and flask neck are dry, then twist and push hard on the rubber stopper to ensure a tight fit. Figure 2: Pressure and Absolute Temperature Experimental Setup 3. For the cold-water bath, pour 150 mL of water in the 600 mL beaker. Place the flask inside the beaker that contains the water. Make sure you hold the flask down so it remains submerged in the water. 4. Pour ice in the beaker containing the flask slowly until it barely reaches the neck of the flask. Avoid getting the rubber stopper wet. Place the temperature probe in the beaker as shown in Figure 2. The temperature should be between 0 °C and 10 °C. Wait at least 60 seconds (or until the pressure and temperature readings stabilize). Once stabilized, record the temperature and pressure readings on your lab notebook. 5. Dump the cold water out of the beaker and dry the flask. 6. Pour 300 mL of room temperature water into the 600 mL beaker. Place the dry flask inside the beaker. Hold down the flask so it remains submerged in the water. The temperature should be between 20 °C and 30 °C. Wait at least 60 seconds (or until the pressure and temperature readings stabilize). Once stabilized, record the temperature and pressure readings on your lab notebook. 7. Discard the water in the beaker and dry the flask. 8. Pour 300 mL of hot water into the 600 mL beaker. Place the dry flask inside the beaker. Hold the beaker down so it remains submerged in the water. The temperature should be between 60 ºC and 70 ºC. Wait at least 60 seconds (or until the pressure and

44 temperature readings stabilize). Once stabilized, record the temperature and pressure readings on your lab notebook. DO NOT discard the hot water. 9. For the final observation, wait for the temperature of the water to be between 40 ºC and 50 ºC. Once the temperature is reached, submerge the flask in the beaker. Wait at least 60 seconds (or until the pressure and temperature readings stabilize). Once stabilized, record the temperature and pressure readings on your lab notebook. 10. Discard the water in the beaker. Disassemble the apparatus and dry the glassware. 11. Graph the temperature and pressure readings using the Excel spreadsheet provided on Canvas. Part III. Volume and Absolute Temperature In this experiment, you will study the relationship between the volume of a gas sample and its absolute temperature. Using the apparatus shown in Figure 3, you will place a 125 mL Erlenmeyer flask containing an air sample in a water bath and you will vary the temperature of the water bath. Data collection will be done as before. Collect the data pair simultaneously from the Gas Pressure Sensor and Temperature Probe, and then record the volume on your lab notebook. Even though the pressure reading will not be plotted on the graph of volume vs. temperature, it is important for pressure to be monitored so that it can be kept constant. 1. Assemble the apparatus shown in Figure 3. Be sure all fittings are air-tight. Make sure the rubber stopper and flask neck are dry, then twist and push hard on the rubber stopper to ensure a tight fit. Be sure that the Luer-lock is opened to the large 60 mL syringe and the volume reads 20 mL. Figure 3: Volume and Absolute Temperature Experimental Setup 2. Fill the pitcher almost halfway with tap water and insert the assembled apparatus. Place the pitcher containing the flask in a large storage bin. This will catch any water overflow from the pitcher. Then, fill the rest of the pitcher with hot water to reach 45-

45 50°C, until it begins to overflow. Hold the apparatus in place by the barrel of the syringe, not the plunger since it will rise to stabilize pressure. Important: The water level must be equal to or higher than the gas level in the syringe (see Figure 3). Once the experiment begins, the apparatus must not be removed from water and the pressure should be kept constant. Wait 5 five minutes or until pressure is constant (within 0.1 or 0.2 kPa) before taking the reading so that the apparatus can get acclimated to the water bath. Collect your data for 60 seconds and record your measurements on the lab notebook for volume and temperature from that last reading (not the average provided in the screen). 3. For the following readings, the temperature should be decreased by ~5 ºC. Add small handfuls of ice to reach the desired temperature. Stir the solution in the pitcher vigorously until the ice dissolves and check the temperature. Repeat as needed. When the suggested temperature is reached and the pressure remains constant (+/- 0.5 kPa), collect data for 60 seconds. Important: If the syringe is not adjusting by itself after 20-30 seconds, slightly press the plunger until pressure matches or gets close to initial pressure (Step 3) then collect the temperature, and volume measurements. If you encounter any problems, consult your GSA. 4. Repeat step 3 for a total of five increments. The minimum solution temperature should be between 25 and 29 ºC. 5. To find the total volume of air in the apparatus, first measure the volume of air in the flask by filling it with water until it reaches the rubber stopper. Pour the water into a 50 mL graduated cylinder. Record this value. For the estimated volume of the tubing (from the rubber stopper to the Gas Pressure Sensor box), as well as in the valve below the bottom of the syringe, use a value of ~4 mL. Finally, add the values from the volumes of the flask, plastic tubing, and syringe all together to calculate the total volume. 6. Graph the values of temperature and volume using the Excel Spreadsheet from Canvas.

46 Properties of Gases Data Sheet Name_______________________________________________________________ Section___________________ Date_____________________ Part I: Pressure and Volume Volume (mL) Pressure (kPa) 15 13 11 09 07 Part II: Pressure and Absolute Temperature Temperature (ºC) Temperature (K) Pressure (kPa) Part III: Volume and Absolute Temperature Volume in the syringe (mL) Total Volume (mL) (refer to step 6) Temperature Range (ºC) Actual Temperature (ºC) Pressure (kPa) 45-50 40-44 35-39 30-34 25-29 Complete the following table: Laws Variables α , 1/ α Constants Boyle Charles Gay-Lussac Write an equation using the two variables using k as the proportionality constant (i.e. P = k x V is direct, or P = k /V if inverse.

47 Properties of Gases Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or rephrase what somebody else writes. Type the report using justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements You must include all graphs from the excel spreadsheet with a brief description of each one. You must also include the tables associated with each graph with a brief description of the table. Discussion Questions 1. Consider the filling of a scuba tank. At constant temperature and volume, what would be the expected effect on pressure (P) if the number of moles of gas n is increased. (5 pts.) Given: The Ideal Gas Law equation is PV=nRT. 2. Why is Kelvin the unit for temperature in the ideal gas law equation? Why is Celsius not used in the ideal gas law equation? (5 pts.) 3. In Part III, as you placed the apparatus in the warm water bath, you should have noticed the volume of air in the syringe increased. What variable in the ideal gas law remained constant? (5 pts.) Given: The Ideal Gas Law equation is PV=nRT.

48 Properties of Gases Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double-spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all.

49 Data & Results 12 points Types up all of the tables and data collected in the Lab. Includes figures. Tables are appropriately labeled (each correctly identified, appropriate title, and units are included), and data is complete. Required figures are also included. Data doesn't match the Lab notebook. Tables are presented incorrectly or not adequately labeled. Data makes no sense, etc. A picture or image of the data sheet or notes taken is given as data results (i.e., screenshots of the Benchling lab notebook). You are missing most or all data and results. Calculations 5 points This section includes typed examples of all designated calculations. Includes a typed example of all calculations performed. Units are included. Some calculations are missing, OR units are missing. A picture or image of the data sheet or notes taken is given as calculations OR none included. Analysis 8 points Brief but thorough explanation of results, trends, and what they mean. Includes a separately labeled section with an explanation of results, trends, and what they mean. Some trends are explained or missing or inadequate explanation. No analysis included. The student writes procedure as analysis. Discussion Question 1 5 points At constant temperature, if n represents the moles of gas present, what would be the expected relationship between pressure (P) and the number of moles of gas (n). Identifies the relationship. Not applicable. Answer is either correct or incorrect. No answer included, or answer does not make sense. Discussion Question 2 5 points From your plot of pressure vs. temperature, why is the unit of temperature in the gas equation Explains why an absolute scale (Kelvin) is used and what would happen if the Explains why an absolute scale (Kelvin) is used OR what would happen if the No answer included, or answer does not make sense.

50 reported in Kelvin? What would happen if degrees Celsius were used? Celsius scale is used. Celsius scale is used. Discussion Question 3 5 points In Part III, as you placed the apparatus in the warm water bath, you should have noticed the volume of air in the syringe increased. Explain what has happened to the gas. What variable should have remained constant? Explains what happened and what variable remained constant. Explains one or the other but not both. No answer included, or answer does not make sense.

51 Experiment 4: Beer’s Law Experiment 4: Beer’s Law

52 Beer’s Law Introduction OBJECTIVES Prepare and measure the absorbance of five standard nickel(II) nitrate solutions. Plot a standard curve from the data obtained from the standard solutions. Measure the absorbance of a nickel(II) nitrate solution of unknown concentration. Calculate the concentration of the unknown Ni(NO 3 ) 2 solution. Background Visible spectroscopy involves shining light on a sample that causes no change to the solution. Colored solutions have interested chemists for a long time. When colored solutions are irradiated with “white” light they selectively absorb light of some wavelengths, but not others. When this happens, the absorbed light disappears and the remaining light (lacking this color) contains the remaining mixture of non-white light wavelengths. A color-wheel (below) shows approximate complementary relationships between wavelengths absorbed and what we see. For example, a green substance, absorbs red light (the complementary color). Image from: http://sustainable-nano.com/2015/07/07/fruit-colors/ We can determine the wavelength or group of wavelengths absorbed by exposing the solution to monochromatic light of different wavelengths and recording the responses. If light of a particular wavelength is passed through a sample and does not reach the detector, we will see that the intensity of the transmitted light (I) is significantly less than the intensity of the light incident on the sample (I o ). The percent transmittance is then defined as the percent of the incident light that passes through the sample such that

53 %T = (I/I o ) x 100 (1) The Beer-Lambert law shows that the molar solution concentration (c) is linearly related to the log of the ratio of the transmitted and incident light, equation 2, where l is the length of sample cell (usually 1 cm) and ε is the molar absorptivity, which is a constant for each particular molecule. log(I o /I ) = εcl (2) This equation is often written in terms of absorbance (A), equation 3. A = εcl (3) With this equation (or a calibration curve based on it), you can (a) determine the concentration of an unknown solution or (b) estimate what the absorbance of a certain solution will be as long as three of the four values in the equation are known. The primary objective of this experiment is to determine the concentration of an unknown nickel (II) nitrate solution. You will use a Vernier SpectroVis spectrometer to measure the concentration of each solution. In this experiment, light from the LED light source will pass through the solution and strike a photocell. A solution of higher concentration absorbs more light (and transmits less) than a solution of lower concentration. The spectrometer monitors the light received by the photocell as percent transmittance. You will prepare five nickel (II) nitrate solutions of known concentrations (these are called standard solutions). Concentration is related to the amount of a substance (nickel (II) nitrate) per volume of water. The typical unit of concentration in chemistry is “molarity,” abbreviated “M.” If you are not familiar with molarity concentrations, that’s OK. Just understand that the molarity of nickel (II) nitrate in a solution is proportional to the amount of nickel (II) nitrate in the solution. The more added, the higher the concentration. Each solution is transferred to a small, rectangular cuvette that is placed into the spectrometer. The amount of light that penetrates the solution and strikes the photocell is used to compute the absorbance of each solution. You will plot absorbance (y-axis) as a function of concentration (x-axis) to get a linear standard curve. Using this standard curve, you will determine the concentration of an unknown Ni(NO 3 ) 2 solution by measuring its absorbance with the spectrometer. You can either use the graph or linear regression obtained from the standard curve information to find the concentration of the unknown solution.

54 Beer’s Law Safety Always wear proper personal protective equipment (i.e., your goggles and lab coat). Always wear proper attire: long pants/skirt with no holes, shoes that completely cover your feet, and keep long hair tied back. Gloves must be worn while handling chemicals. However, gloves must not be worn in the hallways or when interacting with non-chemical entities (e.g., door handles, eyes, or laptops/cell phones). Remove gloves before exiting the lab unless transporting chemicals with the aid of an ungloved partner to open doors. Place your backpacks, skateboards, etc. on the counter in the back of the lab. It is important that people don’t trip and fall when working around hazardous chemicals. You may not wear headphones in the lab because they distract you from your environment created a hazardous lab space. Waste Disposal Dispose of all waste in the oxidizer waste container labeled OX. Disposable face masks and gloves can be thrown in the regular trash.

55 Beer’s Law Experimental Procedures 1. Obtain 15-20 mL of 0.30 M nickel (II) nitrate (Ni(NO 3 ) 2 ) solution in your 25 or 50 mL graduated cylinder. See the video Measuring Stock Solutions for assistance. ( http://youtu.be/bu-r6dAaId0 ) Pour this into a 100 mL beaker. 2. Fill a different 100 mL beaker half full with DI water. 3. Label five clean, dry, test tubes 1-5. 4. Prepare five standard solutions according to the chart below using two droppers. Make sure you don’t mix up your two pipet tes – use one for Ni(NO 3 ) 2 and another for the distilled water. Thoroughly mix each solution with a stirring rod. Clean and dry the stirring rod between uses. Refill your 10 mL graduated cylinders with either Ni(NO 3 ) 2 solution or water as needed. See the video SE1 Nickel (II) Nitrate: Dilutions for assistance. ( http://youtu.be/sO0f7uGkKgs ) Test tube number 0.30 M Ni(NO 3 ) 2 (mL) Distilled H 2 O (mL) 1 1.0 4.0 2 2.0 3.0 3 3.0 2.0 4 4.0 1.0 5 5.0 0 5. Connect a Spectrometer to the USB channel of the Vernier LabQuest unit. Connect the LabQuest unit to the spectrometer using the USB cable. Turn on the LabQuest unit. View the video How to Start the Lab Quest Unit and Spectrometer for assistance. ( http://youtu.be/OCK1PbrZZEE ) 6. Calibrate the spectrometer. a. Prepare a reference (or “blank”) sample by filling an empty cuvette ¾ full with distilled water.

56 b. On the LabQuest unit, tap the reddish-orange meter box and select Calibrate. The following message appe ars in the Calibrate dialog box: “Waiting ... seconds for lamp to warm up.” After the allotted time, the message changes to: “Finish Calibration”. View the video How to Calibrate the Spectrometer for assistance. ( http://youtu.be/S-Pu3G85kew ) c. Place the blank in the cuvette slot of the spectrometer. Notice that the cuvette has two different sides, a smooth side (left) and a ridged side (right). Make sure that the smooth side with the arrow at the top is facing the side of the spectrometer’s cuvette slot with the arrow and light bulb. d. Select “Finish Calibration”. When the message “Calibration Completed” appears after several seconds, select OK. 7. You are now ready to collect absorbance-concentration data for the five standard solutions. First, you must select the wavelength of light to analyze. See the video How to Measure Absorbance of a Solution for assistance. ( http://youtu.be/hvQ3_MqiNZA ) a. Empty the cuvette and rinse it twice with small amounts (< 1 mL) of nickel (II) nitrate solution from test tube 1. Fill the cuvette 3 / 4 full with the solution and place it in the spectrometer. Collect used nickel (II) nitrate solution in a beaker at your workstation to dispose of in the satellite waste area at the end of the experiment - do not pour the solutions down the drain . b. Start the data collection by tapping the green arrow in the bottom of the screen. A full spectrum graph of the solution will be displayed. c. Stop the data collection by tapping the red square at the bottom of the screen.

57 d. Review the graph to identify the peak absorbance value. Use the stylus or the left and right arrow keys to move the cursor to a wavelength of 659 nm (or as close as possible). e. Write down the absorbance and concentration values on your data sheet. f. Empty the cuvette of the used nickel (II) nitrate solution into your beaker at your workstation to dispose of in the satellite waste area at the end of the experiment - do not pour the solutions down the drain . g. Rinse the cuvette with DI water. All rinse water should be collected in your beaker. 8. Repeat step 7 with the remaining standard solutions. Record the absorbance and concentrations of each solution on your data sheet. 9. Graph the data to determine the linear best fit curve for your data. This step can be done after lab. 10. Determine the concentration of the unknown Ni(NO 3 ) 2 solution. a. Record the unknown ID number in your lab notebook. b. Obtain about 5 mL of the unknown Ni(NO 3 ) 2 solution. See the video Measuring Stock Solutions for assistance. ( http://youtu.be/bu-r6dAaId0 ) c. Measure the absorbance as you did for the standard nickel (II) nitrate solutions in step 9. d. Use this absorbance value and the best fit equation from step 9 to solve for the unknown concentration. This step can be done after lab. 11. Clean your cuvette by rinsing it with water. All rinse water should be collected in your beaker. 12. The collected nickel (II) nitrate solutions and rinse water should be disposed of in the oxidizer waste container labeled OX.

58 Beer’s Law Data Sheet Name_______________________________________________________________ Section___________________ Date_____________________ Trial Concentration (mol/L) Absorbance at 659 nm 1 2 3 4 5 0.30 Best-Fit line equation 6 Unknown ID ____

59 Beer’s Law Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or rephrase what somebody else writes. Type the report using justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements Create a graph of absorbance vs. concentration. Add a linear trendline and show the equation. After the graph is complete, copy the graph into your lab report and lab notebook. Do not make graphs by hand, and do not put screenshots or pictures of your graph in your lab report. You must provide the graph and data table in your report to receive full credit. Discussion Questions Copy these questions into the lab notebook for perusal during the lab. Answer these questions in prose (complete sentences, paragraph form) in the lab report. 1. Assume you have two different unknown nickel (II) nitrate solutions in your lab. Without using a spectrometer or any other instrument, how could you estimate which of the unknown nickel (II) nitrate solutions is more concentrated, relative to each other? (5 pts) 2. The color of a cobalt (II) nitrate solution is red. Would you be able to use your nickel (II) nitrate calibration curve to calculate an unknown concentration of cobalt (II) nitrate? Justify your answer. (10 pts)

60 Beer’s Law Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double- spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all. Data & Results 7 points Types up all of the tables and data collected in the Lab. Includes figures. Tables are appropriately labeled (each correctly identified, Data doesn't match the Lab notebook. Tables are presented A picture or image of the data sheet or notes taken is given as data

61 appropriate title, and units are included), and data is complete. Required figures are also included. incorrectly or not adequately labeled. Data makes no sense, etc. results (i.e., screenshots of the Benchling lab notebook). You are missing most or all data and results. Calculations 10 points This section includes typed examples of all designated calculations. Includes a typed example of all calculations performed. Units are included. Some calculations are missing, OR units are missing. A picture or image of the data sheet or notes taken is given as calculations OR none included. Analysis 8 points Brief but thorough explanation of results, trends, and what they mean. Includes a separately labeled section with an explanation of results, trends, and what they mean. Some trends are explained or missing or inadequate explanation. No analysis included. The student writes procedure as analysis. Discussion Question 1 5 points Assume you have two different unknown nickel (II) nitrate solutions in your lab. Without using a spectrometer or any other instrument, how could you estimate which of the unknown nickel (II) nitrate solutions is more concentrated, relative to each other? The student explains their estimation process. Student demonstrates partial understanding. No answer included, or answer does not make sense. Discussion Question 2 10 points The color of a cobalt (II) nitrate solution is red. Would you be able to use your nickel (II) nitrate calibration curve to calculate an unknown concentration of cobalt (II) nitrate? The student understands Beer’s Law and clearly explains the application. The student understands how Beer’s Law can be applied but misunderstood the question. No answer included, or answer does not make sense.

62 Justify your answer.

63 Beer’s Law Calculations Step 1: Calculate the concentrations of your dilutions. (C 1 V 1 =C 2 V 2 ) C 1 = the concentration of Ni(NO 3 ) 2 used V 1 = the volume of Ni(NO 3 ) 2 C 2 = this is what you are solving for V 2 = the total volume of solution Example: C 1 = 0.50M Ni(NO 3 ) 2 V 1 = 5.0 mL C 2 = ? V 2 = 5.0 mL ? 2 = ? 1 × ? 1 ? 2 = 0.50M Ni(?? 3 ) 2 × 5.0 ?? 5.0 ?? = 0.50 ? Ni(?? 3 ) 2 Step 2: Plot absorbance vs concentration. Example graph. Use this calibration curve to solve for concentration by plugging in the measured absorbance of the unknown. A = εl • c + 0 ↓ ↓ ↓ ↓ y = m • x + b ? = ? − ? ? ? = 𝐴 − ? 𝜀?

64 Experiment 5: Determining the Enthalpy of a Chemical Reaction Experiment 5: Determining Enthalpy

65 Determining Enthalpy Introduction Thermochemistry is the branch of chemistry that describes energy changes occurring during chemical transformations. Chemical reactions and phase changes are two notable chemical transformations. As chemical bonds break and form in a chemical reaction, energy in the form of heat ( q rxn ) is either released or absorbed by the reaction (the system ). It is difficult to measure the heat exchange between reactants and products (the system ) directly. However, considering that energy cannot be created or destroyed (1 st law of thermodynamics) we can assume that the energy lost/gained during a chemical transformation is opposite in sign, but equal in magnitude, to the energy gained/lost by the surroundings: 0 = q gained + q lost (1) -q lost = q gained (2) Therefore, we can indirectly measure the heat transfer of the system by measuring the heat transfer that occurs between the system and surroundings. Calorimetry is the measurement of heat associated with a chemical or physical process. The heat exchanged between the system and surroundings can be measured when the chemical or physical change occurs in a calorimeter. A calorimeter is an object which has a known heat capacity determined via calibration. Given that the heat capacity of the calorimeter is known, any temperature change made to the calorimeter can be converted to an amount of heat associated with the chemical/physical process responsible for this temperature change. It is important to define the system in calorimetry as the materials undergoing the chemical/physical change, and the surroundings as the components of the calorimeter responsible for absorbing heat from the system or providing heat to the system In this experiment, you will determine enthalpy changes of chemical reactions ( ΔH rxn ) using “ coffee cup ” calorimetry. Coffee cup calorimetry is performed under constant pressure (isobaric conditions) due to the system being open to the atmosphere. When pressure is held constant, the heat ( q rxn ) released or absorbed during a reaction is equal to the enthalpy change of the reaction ( ΔH rxn ). The derivation of why q rxn =

66 ΔH rxn at constant pressure exceeds the scope of this experiment but is shown for your own understanding below. From the First Law of Thermodynamics the change in internal energy of a system: Δ U sys = q + w (3) Chemical reactions are generally associated with the potential to do electrical work and work of expansion. The former refers to the potential for a chemical reaction to provide an electric current whereas the latter refers to work being done on the surroundings when the volume of a system expands during the reaction. Given that there is no significant electric work done by driving an electric current through an external wire, work of expansion should be considered in calorimetry. The work by expansion is the product of the pressure acting against the system and the volume change in the system. In this case, the expression carries a negative convention as the internal energy U sys decreases because energy is lost to perform work on the surroundings: w expansion = - PΔV (4) Enthalpy (H) was defined to describe the change in heat of a chemical/physical process (system) while work is being done on it. Specifically, it is the sum of the internal energy needed to generate a system and the energy needed by the system to make room for itself by displacing its surroundings upon establishing its own pressure and volume. The change in enthalpy (ΔH) would be written as: ΔH sys = ΔU sys + Δ(PV) sys (5) When considering coffee cup calorimetry where a chemical/physical process occurs under constant pressure, Equation 5 can be written as: ΔH sys = ΔU sys + PΔV sys (6) Using Equation 3 to rewrite ΔU : ΔH sys = Δ(q + w) sys + PΔV sys (7)

67 Given that only w expansion will be significant for the system, w expansion may be treated as total Δ w sys and Equation 4 can be used to rewrite Equation 7 as: ΔH sys = Δq sys + (- PΔV) sys + PΔV sys = Δq sys (8) Thus, one primary advantage of coffee cup calorimetry is that the enthalpy change ( ΔH rxn ) can be determined directly from heat change ( Δ q rxn ) due to constant pressure conditions. The calorimeter insulates the reaction (system) from its surroundings. If heat is released, the reaction is exothermic and ΔH will be negative (Figure 5-1). If heat is absorbed, the reaction is endothermic and ΔH will be positive (Figure 5-2). It is important for calorimeters to offer a nearly adiabatic boundary. The term adiabatic implies there is no pathway for heat to enter or leave the calorimeter. This level of insulation allows for only the heat being released/absorbed by the system to be measured. Figure 5-1. Illustration of coffee cup calorimetry. When the chemical/physical process is exothermic, ΔH = (-), and the heat released by the system to the surroundings increases the temperature of the solution.

68 Figure 5-2. Illustration of coffee cup calorimetry. When the chemical/physical process is endothermic, ΔH = (+), and the heat absorbed by the system from the surroundings decreases the temperature of the solution. In this experiment, you will determine enthalpy changes ( ΔH rxn ) of chemical reactions using “ coffee cup ” calorimetry. If we conduct a reaction between two substances in an aqueous solution, then the heat gained or lost by the solution can be calculated with the following equation: q soln = m sol × C sol × ∆T sol (9) The term q soln represents the heat that is gained or lost by the solution, m sol is the mass of the solution, C sol is the specific heat of the solution, and ∆ T sol is the temperature change of the solution. This experiment will use water as the solvent of the solution. The value of 4.18 J / g ºC may be used as the specific heat of water. Polystyrene cups (Styrofoam™) are good insulators and thus are suitable container components of the calorimeter used in this experiment. The resistance to temperature change or overall quantification of an insulator’s performance can be quantified using thermal conductivity. The thermal conductivity of the polystyrene cup is

69 approximately 0.06 BTU. The thermal conductivity of the glass used to construct your beaker is approximately 1.82 BTU. A smaller quantity for implies the material is a stronger insulator. Thus, polystyrene cups are superior insulators to your glass beakers. However, they may still absorb some of the heat released by a reaction. Thus, the heat transfer from the system to both the water surroundings and the polystyrene cup surroundings should be considered. The heat absorbed by the polystyrene cup can calculated by the following equation: q cup = C cup x ΔT sol (10) The term q cup represents the amount of heat absorbed by the polystyrene cup, C cup is the calibrated heat capacity of the polystyrene cup, and ∆ T sol is the temperature change of the solution. The term C cup is a value determined experimentally through calibration. The calibration measures the change of temperature of the polystyrene cup given known heat changes and further relates the value to ∆ T sol . The value of 22 J/ºC for C cup has already been determined for you. The total heat of the calorimeter q cal includes the heat of all components and thus includes both q soln and q cup : q cal = q soln + q cup (11) Remembering the first law of thermodynamics and Equation 2: -q lost = q gained (2) Therefore, the sum of the heat gained/lost by the solution and the polystyrene cup is equal to the heat lost/gained by the reaction: q soln + q cup = q cal = - q rxn (12) Since coffee cup calorimetry is performed under constant pressure conditions:

70 q rxn = ΔH rxn (13) In this experiment you will experimentally determine the enthalpy change of five reactions. The first three reactions are the acid-base reactions listed below. 1. NaOH( aq ) + HCl( aq ) → NaCl( aq ) + H 2 O( l ) 2. NaOH( aq ) + NH 4 Cl( aq ) → NaCl( aq ) + NH 3 ( aq ) + H 2 O( l ) 3. HCl( aq ) + NH 3 ( aq ) → NH 4 Cl( aq ) In addition to experimentally determining the ΔH rxn for each of these reactions, you can use Hess’s Law to determine the enthalpy change of reaction three above by manipulating reactions one and two to produce a net reaction. You will compare your calculated value of ΔH rxn for reaction three using values from reaction one and reaction two to your experimentally determined value of reaction three itself. Hess’s law states that the total enthalpy change of a reaction is the net sum of all changes. As long as reaction conditions such as temperature and pressure are kept constant, the pathway or number of steps to synthesize a product are independent of each other, and the product will have the same net enthalpy change. The best way to understand this concept is by reviewing the example below. Hess’s Law Example Consider the overall net reaction N 2 H 4(l) + H 2(g) → 2NH 3(g) Reactions which may be considered as independent steps of the net reaction are shown below with their known net enthalpy change: i) N 2 H 4(l) + CH 4 O (l) → CH 2 O (g) + N 2(g) + 3H 2(g) ∆ H = - 37 kJ/mol ii) N 2(g) + 3H 2(g) → 2NH 3(g) ∆ H = - 46 kJ/mol iii) CH 4 O (l) → CH 2 O (g) + H 2(g) ∆ H = - 65 kJ/mol

71 Upon rearrangement of i)-iii) to produce the overall net reaction shown originally, the enthalpy changes of these independent reactions can be used to calculate the enthalpy change of the overall net reaction. The reaction labeled as “iii” will be flipped to list CH 2 O (g) and H 2(g) as reactants. When the reaction is revered, its net enthalpy change is also flipped with regards to its sign: iii) CH 2 O (g) + H 2(g) → CH 4 O (l) ∆ H = + 65 kJ/mol With the rearrangement is “iii” the overall net reaction can now be obtained: N 2 H 4(l) + CH 4 O (l) + N 2(g) + 3H 2(g) + CH 2 O (g) + H 2(g) → CH 2 O (g) + N 2(g) + 3H 2(g) + 2NH 3(g) + CH 4 O (l) By cancelling like terms on either side, the overall net equation is obtained: N 2 H 4(l) + CH 4 O (l) + N 2(g) + 3H 2(g) + CH 2 O (g) + H 2(g) → CH 2 O (g) + N 2(g) + 3H 2(g) + 2NH 3(g) + CH 4 O (l) = N 2 H 4(l) + H 2(g) → 2NH 3(g) Now that these steps have been arranged to create the overall net reaction of interest, the net enthalpy change of each step can be used to create the net enthalpy change of the overall net reaction: ∆ H = ( - 37 kJ/mol) + (- 46 kJ/mol) + (65 kJ/mol) = - 18 kJ/mol Thus, the net enthalpy change of the overall net reaction N 2 H 4(l) + H 2(g) → 2NH 3(g) calculated to be -18 kJ/mol using the net enthalpy changes of other chemical reactions and the pathway to product formation did not affect its net enthalpy of formation. You will also determine ΔHrxn for two additional systems: (1) the dissolution of ammonium nitrate in water and (2) the redox reaction between magnesium powder and hydrochloric acid.

72 Determining Enthalpy Safety Always wear proper personal protective equipment (i.e., your goggles and lab coat). Always wear proper attire: long pants/skirt with no holes, shoes that completely cover your feet, and keep long hair tied back. Gloves must be worn while handling chemicals. However, gloves must not be worn in the hallways or when interacting with non-chemical entities (e.g., door handles, eyes, or laptops/cell phones). Remove gloves before exiting the lab. If transporting chemicals follow the one glove rule and use one gloved hand to carry the materials and one ungloved hand to touch common surfaces such as doorknobs. Place your backpacks, skateboards, etc. on the counter in the back of the lab. It is important that people don’t trip while working with hazardous chemicals. You may not wear headphones in the lab. Handle all reagents with care to avoid contact with skin. They may cause painful burns. If you accidentally spill a solution or get in contact with a solution, notify the GSA immediately . The GSA will help clean up the spill. If the solution used in this experiment contacts your skin, rinse the affected area with water for a minimum of 15 minutes. If you spill a solution on your gloves, remove the contaminated gloves immediately and retrieve a clean pair. m of 15 minutes. Waste Disposal Reaction 1: NaOH( aq ) + HCl( aq ) — > Waste container labeled non-regulated. Reaction 2: NaOH( aq ) + NH 4 Cl( aq ) — > Waste container labeled Ammonia solutions. Reaction 3: HCl( aq ) + NH 3 ( aq ) — > Waste container labeled Ammonia solutions Reaction 4: Dissolved Ammonium Nitrate — > Waste container labeled Oxidizer Reaction 5: Mg( s ) + 2 HCl( aq ) — > Waste container labeled Acid Gloves, disposable face masks, and all other non-chemical waste are disposed of in the normal trash.

73 Determining Enthalpy Experimental Procedures You will only perform each reaction once and this data will be your calorimeter #1 data. The calorimeter #2 data will come from another group. Do not leave before getting this data from another group. Reaction 1. NaOH and HCl NaOH(aq) + HCl(aq) → NaCl(aq) + H 2 O(l) 1. Nest two Styrofoam cups inside of each other to make your calorimeter. Add the magnetic stir bar to the calorimeter (inner cup). 2. Cover the opening of the calorimeter with the aluminum foil. With a pencil tip, pierce a small hole close to the edge of the cup (Figure 1). The hole should be small to avoid heat loss. Figure 1 Figure 2 3. Assemble the ring stand, utility clamp, and stir plate as seen in Figure 2. Place your calorimeter inside the ring holder and rest it on the stir plate. 4. Measure 25 mL of 2.0 M HCl solution with a graduated cylinder. Remove the aluminum foil/or cup lid and pour the HCl solution into the calorimeter. 5. Tightly cover the top of the calorimeter with the aluminum foil/or cup lid. 6. Carefully insert the temperature probe through the punctured hole in the aluminum foil/or cup lid (Figure 1). Secure the temperature probe with the utility clamp (Figure 2). Be careful not to puncture the bottom of the calorimeter.

74 7. Connect the temperature probe to Channel 1 of the LabQuest unit. Plug in the LabQuest, turn it on, and set the data collection time to 180 seconds (3 minutes). 8. Turn on the stir plate. ** The temperature probe is placed carefully to the side of the cup to avoid collisions with the magnetic stir bar, carefully adjust probe if this happens** 9. Stir the HCl solution in the calorimeter for 3 minutes to allow the apparatus to reach thermal equilibrium. 10. While stirring the HCl solution, measure 25 mL of 2.0 M NaOH solution with a clean graduated cylinder. Do not add it to the HCl solution yet. 11. After the HCl solution has been stirred for 3 minutes, record the temperature as the initial temperature of the HCl solution in your lab notebook. 12. Start the LabQuest. Lift the side of the aluminum foil and add the NaOH solution to the calorimeter. Tightly re-cover the opening of the calorimeter with the aluminum foil/or cup lid and allow to stir for 3 minutes. 13. After 3 minutes, record the maximum temperature observed on the LabQuest in your lab notebook. 14. Dispose of the solution in your waste beaker. Rinse the temperature probe, calorimeter, and the stir bar over the waste beaker. Dry the temperature probe, calorimeter, and the stir bar. 15. Calculate ΔH rxn . 16. Dispose of all chemical waste from reaction 1 in the container labeled Non- Regulated. Reaction between NaOH and NH 4 Cl NaOH(aq) + NH 4 Cl(aq ) → NaCl(aq) + NH 3 (aq) + H 2 O(l) 1. Add the magnetic stir bar to of the calorimeters (inner cup) used in the first reaction. 2. Measure 25 mL of 2.0 M NaOH solution with a graduated cylinder. Remove the aluminum foil/or cup lid and pour the NaOH solution into the calorimeter. 3. Tightly cover the top of the calorimeter with the aluminum foil/or cup lid. 4. Carefully insert the temperature probe through the punctured hole in the aluminum foil/or cup lid (Figure 1). Secure the temperature probe with the utility clamp (Figure 2). Be careful not to puncture the bottom of the calorimeter. 5. Connect the temperature probe to Channel 1 of the LabQuest unit. Plug in the LabQuest, turn it on, and set the data collection time to 180 seconds (3 minutes).

75 6. Turn on the stir plate. ** The temperature probe is placed carefully to the side of the cup to avoid collisions with the magnetic stir bar, carefully adjust probe if this happens** 7. Stir the NaOH solution in the calorimeter for 3 minutes to allow the apparatus to reach thermal equilibrium. 8. While stirring the NaOH solution, measure 25 mL of 2.0 M NH 4 Cl solution with a clean graduated cylinder. Do not add it to the NaOH solution yet. 9. After the NaOH solution has been stirred for 3 minutes, record the temperature as the initial temperature of the NaOH solution on your lab notebook. 10. Start the LabQuest. Lift the side of the aluminum foil/or cup lid and add the NH 4 Cl solution to the calorimeter. Tightly re-cover the opening of the calorimeter with the aluminum foil/or cup lid and allow to stir for 3 minutes. 11. After 3 minutes, record the maximum temperature observed on the LabQuest in your lab notebook. 12. Dispose of the solution in your waste beaker. Rinse the temperature probe, calorimeter, and the stir bar over the waste beaker. Dry the temperature probe, calorimeter, and the stir bar. 13. Calculate ΔH rxn . 14. Dispose of all chemical waste from reaction 2 in the container labeled Ammonia Solutions. Reaction between HCl and NH 4 OH HCl(aq) + NH 3 (aq) → NH 4 Cl(aq) 1. Add the magnetic stir bar to the calorimeters (inner cup) used in the first reaction. 2. Measure 25 mL of 2.0 M HCl solution with a graduated cylinder. Remove the aluminum foil/or cup lid and pour the HCl solution into the calorimeter. 3. Tightly cover the top of the calorimeter with the aluminum foil/or cup lid. 4. Carefully insert the temperature probe through the punctured hole in the aluminum foil /or cup lid (Figure 1). Secure the temperature probe with the utility clamp (Figure 2). Be careful not to puncture the bottom of the calorimeter. 5. Connect the temperature probe to Channel 1 of the LabQuest unit. Plug in the LabQuest, turn it on, and set the data collection time to 180 seconds (3 minutes). 6. Turn on the stir plate. ** The temperature probe is placed carefully to the side of the cup to avoid collisions with the magnetic stir bar, carefully adjust probe if this happens**

76 7. Stir the HCl solution in the calorimeter for 3 minutes to allow the apparatus to reach thermal equilibrium. 8. While stirring the HCl solution, measure 25 mL 2.0 M NH 3 solution (NH 3 = NH 4 OH in solution), with a clean graduated cylinder. Do not add it to the HCl solution yet. 9. After the HCl solution has been stirred for 3 minutes, record the temperature as the initial temperature of the HCl solution on your lab notebook. 10. Start the LabQuest. Lift the side of the aluminum foil /or cup lid and add the NH 3 solution to the calorimeter. Tightly re-cover the opening of the calorimeter with the aluminum foil/or cup lid and allow to stir for 3 minutes. 11. After 3 minutes, record the maximum temperature observed on the LabQuest in your lab notebook. 12. Dispose of the solution in your waste beaker. Rinse the temperature probe, calorimeter, and the stir bar over the waste beaker. Dry the temperature probe, calorimeter, and the stir bar. 13. Calculate ΔH rxn . 14. Dispose of all chemical waste from reaction 3 in the container labeled Ammonia Solutions. Heat of Solution for Dissolving Ammonium Nitrate 1. Add the magnetic stir bar to the calorimeters (inner cup) used in the first reaction. 2. Measure 50 mL of deionized room temperature water with a graduated cylinder. Remove the aluminum foil and pour the water into the calorimeter. 3. Tightly cover the top of the calorimeter with the aluminum foil/or cup lid. 4. Carefully insert the temperature probe through the punctured hole in the aluminum foil/or cup lid (Figure 1). Secure the temperature probe with the utility clamp (Figure 2). Be careful not to puncture the bottom of the calorimeter. 5. Connect the temperature probe to Channel 1 of the LabQuest unit. Plug in the LabQuest, turn it on, and set the data collection time to 180 seconds (3 minutes). 6. Turn on the stir plate. ** The temperature probe is placed carefully to the side of the cup to avoid collisions with the magnetic stir bar, carefully adjust probe if this happens** 7. Stir the water in the calorimeter for 3 minutes to allow the apparatus to reach thermal equilibrium. 8. While waiting, use the electronic balance to weigh 2.5 g of ammonium nitrate in a plastic weigh boat.

77 9. After 3 minutes, record the temperature as the initial temperature of the water on your data lab notebook. 10. Start the LabQuest. Lift the side of the aluminum foil/or cup lid and add the ammonium nitrate to the calorimeter. Tightly re-cover the opening of the calorimeter with the aluminum foil/or cup lid and allow to stir for 3 minutes. 11. After 3 minutes, record the minimum temperature observed on the LabQuest in your lab notebook. 12. Dispose of the solution in your waste beaker. Rinse the temperature probe, calorimeter, and the stir bar over the waste beaker. Dry the temperature probe, calorimeter, and the stir bar. 13. Calculate ΔH rxn . 14. Dispose of all chemical waste from reaction 4 in the container labeled Oxidizer. Heat of Reaction for a Redox Reaction 1. Add the magnetic stir bar to the calorimeters (inner cup) used in used in the first reaction. 2. Measure 50 mL of 2.0 M HCl solution with a graduated cylinder. Remove the aluminum foil and pour the HCl solution into the calorimeter. 3. Tightly cover the top of the calorimeter with the aluminum foil/or cup lid. 4. Carefully insert the temperature probe through the punctured hole in the aluminum foil/or cup lid (Figure 1). Secure the temperature probe with the utility clamp (Figure 2). Be careful not to puncture the bottom of the calorimeter. 5. Connect the temperature probe to Channel 1 of the LabQuest unit. Plug in the LabQuest, turn it on, and set the data collection time to 180 seconds (3 minutes). 6. Turn on the stir plate. ** The temperature probe is placed carefully to the side of the cup to avoid collisions with the magnetic stir bar, carefully adjust probe if this happens** 7. Stir the HCl solution in the calorimeter for 3 minutes to allow the apparatus to reach thermal equilibrium. 8. While waiting, use the electronic balance to weigh 0.5 g of magnesium in a plastic weigh boat. 9. After 3 minutes, record the temperature as the initial temperature of the HCl solution in your lab notebook. 10. Start the LabQuest. Lift the side of the aluminum foil/or cup lid and add the magnesium to the calorimeter. Tightly re-cover the opening of the calorimeter with the aluminum foil/or cup lid and allow to stir for 3 minutes.

78 11. After 3 minutes, record the maximum temperature observed on the LabQuest in your lab notebook. 12. Dispose of the solution in your waste beaker. Rinse the temperature probe, calorimeter, and the stir bar over the waste beaker. Dry the temperature probe, calorimeter, and the stir bar. 13. Calculate ΔH rxn . 14. Dispose all of the chemical waste in the container labeled Acid.

79 Determining Enthalpy Data Sheet Names: _______________________________________________________________ Section: ___________ Date: _____________________________ 1. Reaction between NaOH and HCl Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL Initial temperature of HCl prior to mixing, T i (ºC) T f after mixing (highest or lowest T over 3 minutes) (ºC) ΔT (ºC) q soln (kJ) q cup (kJ) q cal (kJ) q rxn (kJ) ΔH rxn (kJ) Average ΔH rxn (kJ) Exothermic or Endothermic?

80 Show sample calculations done on one of the trials for any of the reactions.

81 2. Reaction between NaOH and NH 4 Cl Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL Initial temperature of NaOH prior to mixing, T i (ºC) T f after mixing (highest or lowest T over 3 minutes) (ºC) ΔT (ºC) q soln (kJ) q cup (kJ) q cal (kJ) q rxn (kJ) ΔH rxn (kJ) Average ΔH rxn (kJ) Exothermic or Endothermic?

82 3. Reaction between HCl and NH 4 OH Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL Initial temperature of HCl prior to mixing, T i (ºC) T f after mixing (highest or lowest T over 3 minutes) (ºC) ΔT (ºC) q soln (kJ) q cup (kJ) q cal (kJ) q rxn (kJ) ΔH rxn (kJ) Average ΔH rxn (kJ) Exothermic or Endothermic? Using Hess’s Law and your average ΔH rxn for reactions 1 and 2, what would you have expected ΔHrxn to equal

83 Show all calculations done to determine Hess’s Law. Define the variables of the equations and include units.

84 4. Heat of Solution for Dissolving Ammonium Nitrate Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 Mass of entire solution, (g) (density = 1.0 g/mL) Initial temperature of water prior to mixing, T i (ºC) T f after mixing (highest or lowest T over 3 minutes) (ºC) ΔT (ºC) q soln (kJ) q cup (kJ) q cal (kJ) q rxn (kJ) ΔH rxn (kJ) Average ΔH rxn (kJ) Exothermic or Endothermic?

85 5. Heat of Reaction for a Redox Reaction Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 Mass of entire solution, (g) (density = 1.0 g/mL) Initial temperature of HCl prior to mixing, T i (ºC) T f after mixing (highest or lowest T over 3 minutes) (ºC) ΔT (ºC) q soln (kJ) q cup (kJ) q cal (kJ) q rxn (kJ) ΔH rxn (kJ) Average ΔH rxn (kJ) Exothermic or Endothermic?

86 Determining Enthalpy Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or rephrase what somebody else writes. Type the report using justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements All data tables must be included as well as the calculations you used. You must define the variables and include the Hess’ Law from reaction 3. Don’t forget to identify each of the reactions as either exothermic or endothermic. Discussion Questions Copy these questions into the lab notebook for perusal during the lab. Answer these questions in prose (complete sentences, paragraph form) in the lab report. 1. Why do you use a polystyrene cup to construct the calorimeter rather than a glass beaker for these reactions? (5 pts.) (Hint: Compare thermal conductivities) 2. Balance the chemical equation for the reaction between HCl and Mg. What is the gas evolved as a product by this reaction? (5 pts.) 3. Given that the mass is the same, would the total heat generated be the same if you used Mg s trips instead of Mg powder? Comment on the similarity and/or differences in both the rate and the total heat of the reactions. (5 pts.)

87 Determining Enthalpy Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double- spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all. Data & Results 7 points Types up all of the tables and data collected in the Lab. Includes figures. Tables are appropriately labeled (each correctly identified, appropriate title, and units are included), and data is complete. Data doesn't match the Lab notebook. Tables are presented incorrectly or not adequately labeled. Data makes no sense, A picture or image of the data sheet or notes taken is given as data results (i.e., screenshots of the Benchling lab notebook). You are

88 Required figures are also included. etc. missing most or all data and results. Calculations 10 points This section includes typed examples of all designated calculations. Includes a typed example of all calculations performed. Units are included. Some calculations are missing, OR units are missing. A picture or image of the data sheet or notes taken is given as calculations OR none included. Analysis 8 points Brief but thorough explanation of results, trends, and what they mean. Includes a separately labeled section with an explanation of results, trends, and what they mean. Some trends are explained or missing or inadequate explanation. No analysis included. The student writes procedure as analysis. Discussion Question 1 5 points Why do you use a Styrofoam cup calorimeter instead of a glass beaker for these reactions? (Hint: Compare thermal conductivities) Brief but thorough explanation. Student understands calorimetry but didn’t express the explanation. No answer included, or answer does not make sense. Discussion Question 2 5 points Balance the chemical equation for the reaction between HCl and Mg. What is the gas evolved as a product by this reaction? Accurately balances the chemical equation and identifies the gaseous product. Balances the equation OR identifies the gas. No answer included, or answer does not make sense. Discussion Question 3 5 points Given that the mass is the same, would the total heat generated be the same if you used Mg strips instead of Mg powder? Comment on the similarity and/or differences in both the rate and the total heat of the reactions. Explains both factors affecting the rate and heat. Explains one factor or the other but not both. No answer included, or answer does not make sense.

89 Determining Enthalpy Calculations Table 1: Solving for Enthalpy using a random sample data set. Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 1. Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL 50 50 2. Initial temperature of HCl prior to mixing, T i (ºC) 21.6 20.4 3. T f after mixing (highest or lowest T over 3 minutes) (ºC) 33.5 33.8 ºC 4. ΔT (ºC) 11.9 13.4 5. q soln (kJ) 6. q cup (kJ) 7. q cal (kJ) 8. q rxn (kJ) 9 . ΔH rxn (kJ) Average ΔH rxn (kJ): Exothermic or Endothermic? Calculate the average of the two (2) trials. The first calculation needed is the change in temperature (line 4). These values are shown in Table 1 above. Next, you must calculate the q soln (kJ). Remember to convert the answer from joules (J). To solve for q soln you must use this equation: q soln = m sol × C sol × ∆T sol (9) Remember, the assumption that m sol and C sol for the solution is the same as the water being used as the solvent will be made. q soln = (4.18 J/gºC) x (50 g) x (11.9 ºC) = 2,487.1 J To solve for your answer in kilojoules: (2487.1 J) * (1 kJ / 1000 J) = 2.487 kJ

90 Table 2: Solving for Enthalpy using a random sample data set. Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 1. Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL 50 50 2. Initial temperature of HCl prior to mixing, T i (ºC) 21.6 20.4 3. T f after mixing (highest or lowest T over 3 minutes) (ºC) 33.5 33.8 ºC 4. ΔT (ºC) 11.9 13.4 5. q soln (kJ) 2.487 kJ X 6. q cup (kJ) 7. q cal (kJ) X 8. q rxn (kJ) X 9 . ΔH rxn (kJ) X Average ΔH rxn (kJ) Exothermic or Endothermic? Calculate the average of the two (2) trials. (X means left blank intentionally) Solving for q cup this time will use a manipulation of the C cup equation. This must be done because we cannot use the q gain or q lost in this reaction because we simply do not have that data. Since we know: C cal = q cal / ΔT We can multiply both sides of the equation by ΔT to solve for q cal : q cup = C cup x ΔT sol (10) Where the value of 22 J/ºC for C cup was already determined for you through calibration. Again, your answer here must be in kJ: q cup = (22 J/ºC) x (11.9 ºC) = 261.8 J 261.8 J x (1 kJ / 1000 J) = 0.2618 kJ = q cup Table 3: Solving for Enthalpy using a random sample data set. Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 1. Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL 50 50 2. Initial temperature of HCl prior to mixing, T i (ºC) 21.6 20.4 3. T f after mixing (highest or lowest T over 3 minutes) (ºC) 33.5 33.8 ºC 4. Δ T (ºC) 11.9 13.4 5. q soln (kJ) 2.487 kJ X 6. q cup (kJ) 0.2618 kJ X 7. q cal (kJ)

91 8. q rxn (kJ) X 9 . ΔH rxn (kJ) X Average ΔH rxn (kJ) Exothermic or Endothermic? Calculate the average of the two (2) trials. (X means left blank intentionally) Now q cal can be calculated using the sum of both q soln and q cup . Remember q cal represents the heat of all components of the calorimeter. Thus, both the heat of the solution and the heat of the polystyrene cup should be accounted for. q cal = q soln + q cup (11) q cal = 2.487 kJ + 0.2618 kJ = 2.7488 kJ Given principles of the first law of thermodynamics: q gained = -q lost (2) q cal = - q rxn (12) 2.7488 kJ = - q rxn q rxn = -2.7488 kJ Table 4: Solving for Enthalpy using a random sample data set. Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 1. Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL 50 50 2. Initial temperature of HCl prior to mixing, T i (ºC) 21.6 20.4 3. T f after mixing (highest or lowest T over 3 minutes) (ºC) 33.5 33.8 4. ΔT (ºC) 11.9 13.4 5. q soln (kJ) 2.487 X 6. q cup (kJ) 0.2618 X 7. q cal (kJ) 2.7488 X 7. q rxn (kJ) -2.7488 X 8. ΔH rxn (kJ) X Average ΔH rxn (kJ) Exothermic or Endothermic? Calculate the average of the two (2) trials. (X means left blank intentionally)

92 Since coffee cup calorimetry is performed under constant pressure conditions: Therefore, the heat gained/ lost by the solution and the calorimeter is equal to the heat lost/ gained by the reaction: q rxn = ΔH rxn (13) Table 5: Solving for Enthalpy using a random sample data set. Trial 1 – Calorimeter #1 Trial 2 – Calorimeter #2 1. Mass of entire solution, (g). Hint: Assume the density of both solutions = 1.0 g/mL 50 50 2. Initial temperature of HCl prior to mixing, T i (ºC) 21.6 20.4 3. T f after mixing (highest or lowest T over 3 minutes) (ºC) 33.5 33.8 ºC 4. ΔT (ºC) 11.9 13.4 5. q soln (kJ) 2.487 X 6. q cup (kJ) 0.2618 X 7. q cal (kJ) 2.7488 7. q rxn (kJ) -2.7488 X 8. ΔH rxn (kJ) -2.7488 X Average ΔH rxn (kJ) Exothermic or Endothermic? Calculate the average of the two (2) trials. (X means left blank intentionally)

93 Experiment 6: Cycle of Copper Experiment 6: Cycle of Copper

94 Cycle of Copper Introduction A renowned 19th century chemist described his first experience with chemicals in the following way: “While reading a textbook of chemistry I came upon the statement, "nitric acid acts upon copper." I was getting tired of reading such absurd stuff and I was determined to see what this meant. Copper was more less familiar to me, for copper cents were then in use. I had seen a bottle marked nitric acid on a table in the doctor's office where I was then "doing time." I did not know its peculiarities, but the spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words "act upon" meant. The statement "nitric acid acts upon copper" would be something more than mere words. All was still. In the interest of knowledge, I was even willing to sacrifice one of the few copper cents then in my possession. I put one of them on the table, opened the bottle marked nitric acid, poured some of the liquid on the copper and prepared to make an observation. But what was this wonderful thing which I beheld? The cent was already changed and it was no small change either. A green-blue liquid foamed and fumed over the cent and over the table. The air in the neighborhood of the performance became colored dark red. A great colored cloud arose. This was disagreeable and suffocating. How should I stop this? I tried to get rid of the objectionable mess by picking it up and throwing it out of the window. I learned another fact. Nitric acid not only acts upon copper, but it acts upon fingers. The pain led to another unpremeditated experiment. I drew my fingers across my trousers and another fact was discovered. Nitric acid acts upon trousers. Taking everything into consideration, that was the most impressive experiment and relatively probably the most costly experiment I have ever performed. It was a revelation to me. It resulted in a desire on my part to learn more about that remarkable kind of action. Plainly, the only way to learn about it was to see its results, to experiment, to work in a laboratory.” From F. H. Getman, "The Life of Ira Remsen"; Journal of Chemical Education: Easton, Pennsylvania, 1940; pp 9-10. Chemistry is the study of chemical reactions – the rearrangement of atoms to form new

95 materials. The passage above describes a variety of interesting reactions, some of which you will perform in this experiment. In this experiment, you will perform a sequence of reactions of copper that form a cycle. As you record your observations, try to interpret them in terms of chemical equations. Think about grouping them by reaction type. You will also practice quantitative laboratory techniques by determining the percent recovery of the initial sample of copper. The sequence or reactions in this lab begins and ends with metallic copper Cu(s), representing a closed cycle of copper reactions. Since no copper will be added between the initial and final steps, you can quantify the overall efficiency of the closed cycle using percent recovery. Percent recovery is simply the percentage of starting metallic copper recovered at the end of the cycle. Figure 6-1 below shows an outline of the different chemical species of copper in each of the reactions used by the copper cycle in this experiment. Cu(s) (1) → Cu(NO 3 ) 2 (aq) (2) → Cu(OH) 2 (s) ↑ (5) ↓ (3) CuSO 4 (aq) (4) ← CuO(s) Figure 6-1. An outline of the various species of copper produced by each reaction of the copper cycle used in this experiment. The numbers adjacent to each reaction arrow in Figure 6-1 correspond to the following balanced chemical reactions: (1) Cu(s) + 4HNO 3 (aq) → Cu(NO 3 ) 2 (aq) + 2NO 2 (g) + 2H 2 O(l) (2) Cu(NO 3 ) 2 (aq) + 2 NaOH(aq) → Cu(OH) 2 (s) + 2NaNO 3 (aq) (3) Cu(OH) 2 (s) 𝛥 → CuO(s) + H 2 O(l) (4) CuO(s) + H 2 SO 4 (aq) → CuSO 4 (aq) + H 2 O(l) (5) CuSO 4 (aq) + Zn(s) → ZnSO 4 (aq) + Cu(s) Copper Cycle

96 Four types of reactions are represented here. Reaction (1) represents an example of a general oxidation-reduction (redox) reaction. A redox reaction involves the transfer of electrons, in this case from copper to nitrogen. Reaction (2) is classified as a double- replacement precipitation reaction. Note that the nitrate and hydroxide ions ‘ switch partners ’ to produce the Cu(OH) 2 (s) precipitate. Reaction (3) is a decomposition reaction since upon heating the Cu(OH) 2 (s) is dehydrated, creating two new molecules CuO(s) and H 2 O(l) from a single Cu(OH) 2 molecule (decomposes). Reaction (4) is an example of an acid-base neutralization reaction. The CuO(s) metal oxide acts as a base which is neutralized by H 2 SO 4 (aq) to form a salt (CuSO 4 (aq)) and water. Reaction (5) is a single-replacement reaction where Zn displaces Cu to form ZnSO 4 (aq) and Cu(s). Single-replacement reactions are also redox reactions as the two participating elements undergo redox changes while transitioning to and from each of their free elemental (oxidation number =0) states. In this specific redox reaction Zn is oxidized (loses electrons) and Cu is reduced (gains electrons). This experiment requires you to successfully complete the following: • Follow the procedure attentively to both recover all copper and work safely with hazardous chemicals. • Record detailed observations about each reaction. • Perform calculations using the recorded results.

97 Cycle of Copper Safety Personal protective equipment (PPE) must be worn: goggles, lab coat, and gloves. Always wear proper attire: long pants/skirt (no holes) and close-toed shoes. If applicable, keep long- hair tied back. Gloves must be worn while handling chemicals but remember to remove gloves before exiting the lab. Place your backpacks, skateboards, etc. on the counter in the back of the lab. You will perform every step of this experiment in a fume hood. This is essential for protecting the user from gaseous irritants formed during this experiment. If you accidentally spill a chemical solution in the lab or on yourself during this experiment, notify the GSA immediately . The GSA will clean up the spill in the lab. If the solution gets on your hands wash them for 15 minutes with soap and water. If your gloves contact a solution: remove the contaminated gloves, wash your hands, and retrieve a new pair of gloves. Waste Disposal Step 12: Dispose the aqueous waste in your waste beaker into the container labeled Oxidizer . Optional step 16: If this step is needed, dispose of all aqueous waste in your waste beaker in the container labeled Acid . Step 17: Dispose of all aqueous waste in your waste beaker in the container labeled non- regulated . Step 18: Dispose of the methanol in the waste container labeled non-halogenated . Step 21: Dispose of the solid copper product in the regular trash .

98 Cycle of Copper Experimental Procedures Record your observations for each question (denoted by [ # ] notation) in your Lab Notebook . 1. Fill a 600 mL beaker to the 400 mL mark with tap water. Heat the beaker of tap water on a hot plate in the fume hood to 75-80 °C. The hot plate should be set between a power of “ 6 ” and “ 7. ” Periodically check the temperature of the hot water bath to ensure it is not heating beyond 80 °C. The hot water bath should not boil. 2. Record the mass of a 125 mL Erlenmeyer flask in your lab notebook. 3. Tare the balance with the Erlenmeyer flask. Add 0.38 – 0.42 grams of copper granules to the Erlenmeyer flask. Record the exact mass of the copper granules used in your lab notebook. 4. IN THE FUME HOOD: When the water bath has reached the desired temperature range notify your GSA. Your GSA will provide the nitric acid needed for this reaction. Add 10 mL of 5.0 M nitric acid (HNO3) to the 125 mL copper granule containing Erlenmeyer flask. 5. Allow the Erlenmeyer flask to heat in the water bath for 45 seconds. Remove the Erlenmeyer flask while wearing a heat resistant glove, slowly swirl the solution, and place the flask back in the water bath. Keep repeating this step until all copper granules have dissolved. Record your observations in the lab notebook. [1] What products are present is in the solution once the reaction is complete? Record your observations in the lab notebook. 6. Once the copper granules have completely dissolved, remove the Erlenmeyer flask from the water bath while wearing heat resistant gloves. Allow the Erlenmeyer flask to cool to room temperature in the fume hood. Turn off the hot plate and allow the water bath to cool. Remove the hot water bath from the hot plate while wearing heat resistant gloves. Once the water bath has cooled in the fume hood, dispose of the tap water down the drain. 7. Once the reaction mixture has cooled to room temperature, add 10 mL of deionized water to the Erlenmeyer flask.

99 8. Measure 15.0 mL of 3.0 M NaOH using a graduated cylinder. In a fume hood: Add 15 mL of 3.0 M NaOH to the Erlenmeyer flask and stir with a glass stir rod until the Cu(OH) 2 precipitate has formed. [2] Reference the balanced chemical equation for Reaction (2) above. In addition to Cu(OH) 2 , what other chemical product formed in the solution? Record your observations in the lab notebook. 9. Place the Erlenmeyer flask containing the reaction mixture directly on the hot plate. Set the heating power setting to “ 6. ” Gently heat the reaction mixture without boiling. Stir the reaction mixture with a glass stir rod to prevent bumping (the formation of a large steam bubble and expulsion of solution in a locally overheated area). Record observations in your lab notebook. If your solution begins to boil, remove the Erlenmeyer flask using a heat resistant glove or a test tube clamp and set it on the counter. Turn off the hot plate. 10. Once the transformation is complete, remove the Erlenmeyer flask from the hot plate using a heat resistant glove or a test tube clamp and continue stirring with a glass stir rod for one minute on the bench. Subsequently, allow the reaction mixture to rest until the solid material has settled. 11. Once the solids have settled, decant (pour off) the supernatant liquid into a 600 mL waste beaker at your bench. Be careful to not lose any solid. If you need more space this can be done outside of the hood. See the video Decantation for assistance. ( http://youtu.be/Xassu5TBFDs ). 12. Add approximately 100 mL of hot deionized water to the solids in the Erlenmeyer flask. Allow the solid to settle again and decant once more into the waste beaker. If you need more space this can be done outside of the hood. Dispose of all aqueous oxidizer waste from your waste beaker in the container labeled Oxidizer . [3] Consider both Reaction (2) and Reaction (3). Which products are removed during the washing and decantation steps (steps #11 - #12)? Record your observations in the lab notebook. 13. Carefully measure 15.0 mL of 2.0 M H 2 SO 4 using a graduated cylinder. In a fume

100 hood: Add 15.0 mL of 2.0 M H 2 SO 4 the Erlenmeyer flask containing the solids. Stir the reaction mixture thoroughly with a glass stir rod. [4] What products were formed upon the addition of H 2 SO 4 in step #13? Record your observations on the lab notebook. 14. Weigh 1.5-2.0 grams of metallic zinc powder using a weigh boat. In a fume hood: Add the metallic zinc metal powder to the Erlenmeyer flask containing the solid solution from step #13. Stir the reaction mixture with a glass stir rod until the supernatant liquid becomes transparent, or very pale. If the metallic zinc powder clumps in the solution, break apart the clumps with a glass stir rod. [5] What type of reaction is Reaction (5)? [6] Which element is being oxidized and which element is being reduced in Reaction (5)? Record your observations on the lab notebook. 15. Once any evolution of gas has ceased, decant the supernatant liquid into a waste beaker. 16. If you see any ‘ silvery ’ grains of unreacted metallic Zn mixed with your recovered metallic Cu, add 5 mL of 2.0 M HCl in a fume hood and gently heat (do not boil) the solution. Once the evolution of gas has ceased, allow the solution to cool on the bench inside the fume hood. Decant the cooled supernatant liquid into the waste beaker. If this step is needed, dispose of the aqueous waste from your waste beaker in the container labeled Acid . 17. Wash the recovered metallic Cu with approximately 5 mL of deionized water. Allow the solids to settle and then decant the supernatant liquid into a waste beaker. Repeat the washing and decantation steps at least twice. Dispose of the aqueous waste from your waste beaker in the container labeled non-regulated . 18. In a fume hood: Wash the recovered metallic Cu with approximately 5 mL of methanol. Allow the solids to settle and then decant the methanol. Dispose of the methanol from your waste beaker in the waste container labeled non- halogenated . 19. Heat the Erlenmeyer flask on a hot plate to dry the recover metallic Cu (setting “ 6 ” ). Remove the Erlenmeyer flask from the hot plate using a heat resistant glove or a test tube clamp. Set it on the bench top to cool.

101 [7] What color is the recovered metallic Cu? Does it resemble your starting material from step #1? Record your observations on the lab notebook. 20. Once the Erlenmeyer flask has cooled, weigh the Erlenmeyer flask containing the recovered metallic Cu solids. Record the mass on your lab notebook. Subtract the recorded mass of the empty Erlenmeyer flask from step #1 to calculate the mass of recovered metallic Cu. 21. Clean up your work area. Dispose of the solid copper product in the regular trash . 22. Return all borrowed equipment to the stockroom. A significant portion of this laboratory procedure was taken from Ken Ostrowski’s website, www.ostrowskiness.com/sections/chemistry/HTMLLab/gclab1-06.htm . Used with permission.

102 Cycle of Copper Data Sheet Name_______________________________________________________________ Section___________________ Date_____________________ Table 1: Data Table of Mass and Recovery Values Measured Mass Units (g) Erlenmeyer flask (Step 1) Copper granules (Step 2) Erlenmeyer flask and dry copper (Step 20) Mass of recovered copper Percent recovery of metallic Cu Calculation: % recovery Below are the same questions asked in various parts of the procedure. The answers to these questions must be recorded in your lab notebook and in the analysis of results section of the lab report. Step 5: [1] What products are present is in the solution once the reaction is complete? Step 8: [2] Reference the balanced chemical equation for Reaction (2) above. In addition to Cu(OH) 2 , what other chemical product formed in the solution? Step 12: [3] Consider both Reaction (2) and Reaction (3). Which products are removed during the washing and decantation steps (step #11 - #12)? Step 13: [4] Which products were formed upon the addition of H 2 SO 4 in step #13? Step 14: [5] What type of reaction is Reaction (5)? [6] Which gas is produced by Reaction (5)? Step 19: [7] What color is the recovered metallic Cu? Does it resemble your starting material from step #1? Table 2: Observations from reactions in the copper cycle Reaction Observations Cu + HNO 3 Cu(NO 3 ) 2 + NaOH Cu(OH) 2 + heat

103 CuO + H 2 SO 4 CuSO 4 + Zn

104 Cycle of Copper Report Requirements Standard Report Requirements Each student will write a short report for this experiment. Write everything in your own words. Do not copy or paraphrase what somebody else writes. Type the report using a justified alignment, double spacing, 1-inch margins, and Times New Roman 12-point font or Arial 11-point font. It should include the following sections: Header, objectives, procedures, data and results, analysis, calculations, and discussion. Experiment Specific Requirements Answers to the questions in the procedure should appear in the Results section of your report as a table. Please be detailed. In the analysis include a brief explanation of your percent recovery. How much of the starting copper were you able to recover at the end? Calculate the mass of the product you recovered by subtracting the weight of the empty Erlenmeyer flask from the weight of the flask plus the copper metal. Calculate the percent recovery using this equation % ???????? = ?𝑎?? ?? 𝐶?(?) ????????? ??𝑖?𝑖?𝑎? ?𝑎?? ?? 𝐶?(?) ??𝑎????? × 100 % (6.1) Discussion Questions Copy these questions into your lab notebook for use during the experiment. Answer these questions appropriately (complete sentences, paragraph form) in the lab report. 1. Identify the different types, or classification, of the reactions used during the experiment. Classify each specific reaction [Reaction (1), Reaction (2), etc.]. (10 pts.) 2. Would it be physically possible to obtain a percent recovery greater than 100%? Justify your answer. (5 pts.) 3. Which element is being oxidized and which element is being reduced in Reaction (5)? Explain. (5 pts.)

105 Cycle of Copper Report Rubric Section Criteria Full Credit Half Credit No Credit Formatting 3 points Follows report guidelines (justified text, double-spaced, 1-inch margins, single font/color/size). The student followed all formatting guidelines. The student did not follow one or two formatting guidelines. The student did not follow formatting guidelines. The student did not follow three or more formatting guidelines. Prose 1 point The report is written in prose or paragraph form (i.e., no bulleted lists and no numbered lists). The report was written entirely in prose. The report contains some prose and some lists. No prose or paragraphs. Grammar 1 point Correct English grammar, spelling, and use of the third person (i.e., no I, you, we, etc.) No more than 5 typos or grammatical errors. The student uses the third person. No more than 10 typos or grammatical errors. Some use of personal pronouns. Barely readable. Header 2 points Follows header guidelines (student name, lab partner(s) name, date the experiment was performed, lab title). All header guidelines were followed. The students did not follow one or two header guidelines were not followed. The student did not follow header guidelines. The student did not follow three or more header guidelines. Objectives 2 points The objective is a brief description of the purpose of the experiment. The student understands what the experiment was about and why they did it. The student does not quite show understanding of the experiment. No objective included. The objective does not make sense. Procedures 1 point Writes procedures were followed as written in the lab notebook. Includes standard entry unless significant changes were made. The student includes insignificant changes. Includes a detailed procedure or does not include this section at all.