Lab 3 SCC 251 Isolation of Caffeine from Tea Leaves

A student performs a crystallization on an impure sample of biphenyl. The sample weighs 0.5 g and contains about 5% impurity. Based on his knowledge of solubility, the student decides to use benzene as the solvent. After crystallization, the crystals are dried and the nal weight is found to be 0.02 g. Assume that all steps in the crystallization are performed correctly, there are no spills, and the student lost very little solid on any glassware or in any of the transfers. Why is the recovery so low?

How do you separate sodium hydroxide from the crude mixture?

Table 1. Solubility Tests. Functional Group Observations (specify type if any) Sample in concentrated (+/-) H2SO4 Color orange Hydroxyl group Hydroxyl group Hydroxyl group 1-butanol Color orange 2-butanol Color orange diisopropyl ether Look at the structures of compounds tested for solubility in concentrated H2SO4. What generalization can be made for a substance to be soluble in concentrated H2SO4 ?

To which sample solution the spike will be add?  the distillate>130C the mass standard the distilled <130C

Stoichiometry: Prolonged exposure of some functionalities to the eluent (methanol) in this experiment may lead to undesirable reactions. In one case, Acetylsalicylic acid (Aspirin) can react with methanol to form salicylic acid and methyl acetate. If 800 mg of Acetylsalicylic acid and 1 mL of Methanol undergoes such a side reaction (known as "Methanolysis") to completion: (a) write a balanced equation (draw all molecules instead of writing chemical formulas), (b) what is the limiting reagent? (c) predict the grams of salicylic acid and methyl acetate to be produced in this process. Show calculations. Hint: you can determine the grams of 1 mL of Methanol through its density.

Tom, an analytical chemist, bought a bag of decaffeinated coffee from a grocery store. However,Tom suspected that he might have received regular coffee and therefore decided to analyze hiscoffee for caffeine. In the lab, he took 0.5 mL of the brewed coffee and diluted it in water tomake a 100.0 mL solution. He performed four analyses and found the concentrations to be 4.69,3.99, 4.12, and 4.50 mg/L, respectively. (Assume the density of all solutions is 1.000 g/mL,1oz= 28.35 mL).(a) Report the concentration (in mg/L) of caffeine in the brewed coffee using the format asaverage ± standard deviation. (Note this is not the concentration in the diluted solution.)(b) Look up the caffeine content of regular vs. decaffeinated coffee. Do you think that Tom wasgiven the wrong type of coffee?(c) Caffeine intake of 300 mg per day reportedly has no adverse effects in the vast majority ofthe adult population. If Tom drinks 3 cups (8 oz/cup) of this coffee daily, is his intake withinthis known safe…

Series 9. Mixtures Brass Sand + CuSO4• 5H2O White wine Series 9. Mixtures (continued) Water and BaSO4 Oil and water Vinegar

1. Several procedures for the analysis of caffeine involve extracting the caffeine into an organic non-polar solvent (such as methylene chloride CH2Cl2). This about your experiment and what is discussed in the introduction. What might the advantage be for this approach? What is a disadvantage? 2. Think about what you said in the question above. If your sample was espresso, would your answer change? Why? 3. I was careless and ended up using a wavelength other than the peak (Say 250 nm). Would I still be able to carry out the experiment successfully? What might be the reason that I do not get optimum results? 4. I carried out the experiment using a scratched (or several scratches) cuvet for one standard, and clear cuvets for others. How might my calibration curve change (improve or get worse and why)? Pllllz answer these questions as soon as possible

3. Describe the characteristics that a crystal obtained through recrystallization must have, the final crystal, not the solvent.

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Addition of the hot water dissolves some of the precipitate, but some white precipitate still remains on the bottom of the test tube.   Which of the following is a valid conclusion to draw at this point?     Pb2+ is definitely present.   Hg22+ is definitely present.   Ag+ could be present, or Hg22+ could be present, or BOTH could be present.   Ag+ is definitely present

You are tasked with performing a recrystallization. You have 3 potential solvents to use, but you don't know which one will work. How will you go about deciding which solvent to use?

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Upon addition of the hot water, you have some white precipitate still at the bottom of the test tube, and the supernatant liquid is poured off.  To this liquid, potassium chromate (K2CrO4) is added.  Upon this addition of potassium chromate, you observe no formation of precipitate. Which of the following is a valid conclusion to draw at this point? (Choose one.)   Select one:   1. Hg22+ is definitely present.   2. Pb2+ is NOT present. 3. Ag+ is definitely present. 4. Pb2+ is definitely present.

A student dissolved 4 drops of an unknown compound in 1 mL of methylene chloride (dichloromethane) in a test tube. They added 5 drops of a 2% solution of bromine in dichloromethane dropwise and mixed the contents within the test tube gently. They observed the red-brown color discharges (turns colorless) until the last drop. What compound is most likely the unknown? ©GMU 2020 Oa. Methanol b. Cyclohexane c. n-Butyl Bromide O d. Hex-2-ene COLE QUESTION 6 A student placed 2 drops of an unknown sample in a test tube and added 2 mL of ethanol to the test tube while mixing gently. They added 2 drops of potassium permanganate reagent to the test tube and mixed the contents of the test tube gently. The initial color was a deep purple but then changed to a yellow color which precipitates as a brown solid. What compound is most likely the unknown? OGMU 2020 a. Cyclopentane O b. Cyclohexene c. 1-Pentyl Chloride d. 2-Propanol SOUL QUESTION 7 A student performed the Beilstein test within a chemical…

Using recrystallization techniques, a student attempts to purify 0.50 g of compound H. Based on the solubility of H in the chosen solvent at collection temperature, the maximum percent recovery is 82%. The student obtains 0.396 g of purified crystals. What is their percent recovery? Group of answer choices 41% 64% 79% 82% 97% none of these

A mixture of the two compounds shown below is dissolved in ether. Using the information given in the experiment, select all the correct statements regarding the extraction and isolation of the two compounds. X "NH₂ OA. X can be extracted from the organic layer using sodium hydroxide. О в. Y can be extracted from the organic layer using sodium hydroxide. OH Y OC. X can precipitate out of the aqueous layer by the addition of sodium hydroxide to the salt of X. OD. Y can precipitate out of the aqueous layer by the addition of sodium hydroxide to the salt of Y.

b) Will the sample be contaminated with any of the impurities? Calculate the percent purity of the initial sample (in terms of compound A) - ( i.e. express the amount of compound A in the initial sample as a percentage of the mass of initial sample). Calculate the percent purity of the final sample (in terms of compound A) - (i.e. express the amount of compound A in the final sample as a percentage of the mass of final sample). Did the recrystallization procedure result in an increase of the percent purity of compound A in the sample? Comment on the results.

DATA AND CALCULATIONS Show all calculations neatly on an attached sheet. Trial 1 Trial 2 Trial 3 70.6849. 68.0749 2.61g 23.25ML O.65ML 22.6mL Mass of flask + vinegar Mass of empty flask Mass of vinegar used Final buret reading Initial buret reading Volume of NaOH used Moles of NaOH used 0.00226 mol Moles of açetic acid titrated Mass of acetic acid titrated Mass % acetic acid in vinegar 5.0%

5.0 mL of 1-butanol was mixed with 10 mL of HCl. The reaction was put on an ice bath and 4 mL of concentrated sulfuric acid was added. This mixture was refluxed for 45 min and then the product was co-distilled with water using a simple distillation apparatus. Water and the product are immiscible. 1-butanol has a molar mass of 74.12 g/mol, a density of 0.810 g/mL, and a boiling point of 118 C. The product has a molar mass of 92.57 g/mol, a density of 0.880 g/mL, and a boiling point of 78 C. What is the nucleophile in this reaction? What is the role of H2SO4 in this reaction? Calculate the theoretical yield for this reaction. Give your answer in grams.  Select the following statements that can be said about the reaction shown.

Which one answer does NOT represent a characteristic of a good recrystallizing solvent? O 1) Should not react with sample. O 2) Should do a poor job of dissolving impurities when hot. O 3) Should have a moderate boiling point. O 4) Should do a good job dissolving a sample when cold.

experiment A pair of 100 mL samples of water are taken from a well bored into a large underground salt (NaCl) deposit. Sample #1 is from the top of the well, and is initially at 32 °C. Sample #2 is from a depth of 50. m, and is initially at 42 °C. Both samples are allowed to come to room temperature (20. °C) and 1 atm pressure. An NaCl precipitate is seen to form in Sample #1. Two 250 mL samples of water are drawn from a deep well bored into a large underground salt (NaCl) deposit. Sample #1 is from the top of the well, and is initially at 42 °C. Sample #2 is from a depth of 150 m, and is initially at 8 °C. Both samples are allowed to come to room temperature (20 °C) and 1 atm pressure. An NaCl precipitate is seen to form in Sample #1. predicted observation (choose one) A bigger mass of NaCl precipitate will form in Sample #2. A smaller mass of NaCl precipitate will form in Sample #2. The same mass of NaCl precipitate will form in Sample #2. No precipitate will form in Sample #2. I…

How do fill in the Flow Diagram for the Mixtures using the information presented?

Can you solve and complete this chart

3. What is the major obstacle that fractional distillation overcomes? 1 1° in422 male distillatio

Can I get detailed explanation for this table , mentioning the apparatus and when’s the timer is started ? What happens next