Chem142_Calib_Report_Gradescope_021819_MAC-1

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CHEM 142

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Feb 20, 2024

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Name: Abel Tecomahua Quiz Section CK Lab Partner: Nick Strable Student ID #: 2229544 CHEM 142 Experiment #4: Calibration Curves and an Application of Beer's Law Goals of this lab: • Apply the use of a calibration curve to finding the concentration of an unknown • Apply the mechanics of dimensional analysis to calculate the mass of iron in a sample based on concentration of an iron-containing solution • Develop lab skills in operating digital pipettes, volumetric glassware, and spectrophotometers • Use Excel to graphically represent and interpret experimental data • Asses the accuracy of experimental data (compared to a known value) and identify sources of error Your lab report will be grade on the following criteria using a poor/good/excellent rating system (see the Lab 4 Self-Assessment for more details): • Calculations are complete and correct, with proper use of significant figures and units • Data and results are careful and accurate • Lab report is clear, legible, and neat • Error analysis is well-supported and valid • All graphs and tables and clearly and accurately labeled; entire report is typed • Application of skills to new situations is accurate and complete By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will result in 5 points being deducted from your lab score. Signature: ____Abel Tecomahua____________________________________ This lab is worth 60 points: 10 points for notebook pages, 50 points for the lab report (Do NOT include your notebook pages when you scan your report for upload into Gradescope.)

NAME: QUIZ SECTION: DATA, GRAPHS AND CALCULATIONS Creating the calibration curve: l max for absorbance measurments: 515.8 nm (from Part III. B.) Ferroin Standards: Concentration (M) Absorbance (from Part III. C.) 1.25E-05 0.164 2.50E-05 0.32 3.75E-05 0.439 5.00E-05 0.56 6.25E-05 0.677 Slope of Absorbance versus concentration graph 10128 M -1 (enter #s here so the data y-intercept of Absorbance versus concentration graph will correctly autofill on pg 3) 0.052 Detailed calibration equation: (review the introductory information in the lab manual for an explanation of what is meant by a "detailed" calibration equation) Determining the Amount of Iron in an Iron Tablet 1) Average mass of a tablet 463 mg 2) Mass of crushed tablet used in analysis 64.0 mg (enter a # here so the data will correctly autofill on pg 3) 3) 100 is diluted in volumetric flask (lab manual Part II, Step 5) 4) Volume of diluted crushed tablet solution 4.5 mL transferred to the new volumetric flask (lab manual Part II, Step 6) 5) Final volume of ferroin complex solution 100 mL (lab manual Part II, Step 9) 6) Absorbance of the ferroin complex solution 0.342 (enter a # here so the data (lab manual Part III, Step C.7) will correctly autofill on pg 3) Final volume after filtered crushed tablet solution y=10128[ferrion(M)]+0.0522 Note: All sections of this report must be typed y = 10128x + 0.0522 R² = 0.9966 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.00E+00 1.00E-05 2.00E-05 3.00E-05 4.00E-05 5.00E-05 6.00E-05 7.00E-05 Absorbance@ 515.8nm Ferrion Concentration(M) Absorbance vs Concentration

NAME: QUIZ SECTION: Student- specific data from pg 2 used in calculations autofill here on this page: Calib. Curve slope: 10128 y-int of Calib. Curve: 0.052 Absorbance of digested sample: 0.342 Mass crushed tablet: 64.0 7) 8) 9) 10) 11) 12) mg of iron per tablet (as listed on the bottle) 27 mg Using the calibration equation and the absorbance you measured for the prepared sample, calculate the ferroin concentration. Show your work and don't forget to include units. Abs=(12464M x[ferroin M])-0.019 0.250=(14190x[ferroin])-0.019 0.269=(12464x[ferroin]) 2.28x10-5=[ferroin] Based on the procedural steps and the ferroin concentration you just calculated, calculate the moles of ferroin in the final ferroin complex solution prepared in Part II, Step 9. Show your work, including units. 100mL/103 =0.1L 0.1L*2.28x10-5=2.28x10-6 mol Fe Based on the moles of ferroin in the final ferroin complex solution, calculate the moles of iron in the crushed tablet solution prepared in Part II, Steps 2-5. Show your work, including units. (2.28x10-6 moles of ferroin) x (1 mol Fe2+) / (1mol ferroin) x (100mL of original solution) / 5mL of orginal solution = 2.56x10-5 moles of iron Using the "moles of iron in the crushed tablet solution" you just calculated, calculate the mass (in mg) of iron in the crushed sample that you weighed out. Show your work, including units. 2.56x10-5 moles of iron x (55.85g of Fe2+) / (1 mol Fe2+) x (1000)= 1.59mg From the mass of iron in the crushed tablet sample you weighed out, calculate the mass (in mg) of iron in a whole tablet. Show your work, including units. Mass of Fe=1.598 mg x (436mg/64mg) Mass of Fe= 10.89 mg Results and Discussion 1. Compare your mass of iron per tablet with the amount listed on the bottle label. Calculate the % error and discuss YOUR major sources of error. How did this affect your results? ((27mg- 10.89mg) / 27) x 100 = 40.3% There are numerous places where mistakes could have been made. I had trouble getting the podwer to remain on the paper when measuring out the iron powder and had to repeat the process a couple of times. We both have problems with the volumetric pipet. Before asking my spouse to attempt, I tried several times myself. After approximately five tries, she eventually got it near enough to the line, but we might still have been off by that amount. There were numerous areas in this experiment that may have been slightly inaccurate, which would have had a significant impact on the percent error.

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NAME: QUIZ SECTION: 2. If you did not wait for the complete formation of the ferroin complex in Part II, step 10, how would your Abs data be different? Explain how would this affect your determination of the mass of iron in the tablet? Our results would have been considerably different if we hadn't waited the entire five minutes necessary for the ferroin complex to fully develop. Because the reaction wouldn't be finished, the absorption rate would be decreased . 3. You use atomic emission spectroscopy, another spectroscopic technique, to measure the Li + concentration in 5 standard solutions of varying concentrations of LiCl. The intensities for the standard solutions are plotted versus the concentrations and the resulting calibration equation is: Intensity = 82,985 M -1 * [Li + ] + 2.15 If the intensity of your unknown sample is 132, what is the concentration of Li + in the analyzed sample? Li+= (132-2.15) / 82, 985 = 0.0015647= 0.0016 M If 15 mL of the original unknown sample was diluted to 375 mL prior to analysis, what is the concentration of Li + in the original solution? (0.0016 moles Li+) x (0.375L/0.015L)= 0.04M Li+ Laboratory Waste Evaluation Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer drain, thrown in the garbage, collected in a container for disposal by the UW Environmental Health & Safety department, or released into the environment. Based on the written lab procedure and your actions during the lab, list the identity and approximate amount (mass or volume) of waste that you generated while performing this experiment. 64 mg Fe2+ powder 4 mL of .1 HCl 2mL of .23M hydroxylamine hydrochloride 1mL of 1M sodium Acetate 5 mL of 3.6x10-3 M 1,10- phenanthroline 700 or so mL of DI water most in various diluted solutions