Question

1. While synthesizing aspirin, a student masses out 3.4898 g salicylic acid.

A) What is the theoretical yield of aspirin the student can make? (the molar mass of salicylic acid is 138.12 g/mol and molar mass of aspirin is 180.2 g/mol)

B) After vacuum filtration, the student collects 3.8929 g aspirin. What is the percent yield?

C) What is the percent error?

2. What is the yield of aspirin when reacting excess salicylic acid with 2.09 mL of acetic anhydride? The density of acetic anhydride is 1.082 g/mL.

3. What is the percent yield if you prepared 2.80 x 10 3 g of aspirin from an industrial process when the theoretical yield was 3.87 kg?

4. A) Explain how the FeCl3 test helps you determine the purity of aspirin (What functional group causes the reaction)?

B) After reviewing the results of the FeCl3 test that your lab instructors posted, what is the purest aspirin product, the commercial aspirin or the synthesized aspirin? Why?

C) Propose a reason for your observation for part B.

D) What was the purpose of testing ethanol with FeCl3?

5. A) What functional group(s) is/are responsible for the acidity of aspirin?

B) According to the pH test results posted by your instructors, what is the sample that is most acidic? And why?

C) Why do you propose that we convert Salicylic acid to Acetylsalicylic acid although they both function as analgesics?

Answer 1

1. Theoretcial yield is defined as the amount of product formed by the complete reaction of the given reactant.

The chemical reaction for the synthesis of aspirin from salicylic acid is given by,

Acetic Anhydride + Salicylic Acid → Aspirin + Acetic Acid

From the reaction it is identified that one mole of salicylic acid gives one mole of aspirin.

The number of moles of salicylic acid is calculated to be,

Thus 0.025 mol of salicylic acid gives 0.025 mol aspirin.

Thus theoretical yield of aspirin = 4.55 g.

1. Percent yield is the percent ratio of theoretical yield to actual yield.

  

Thus percent yield of aspirin = 116.95%.

1. Percent error is the difference between theoretical and actual value divided by actual value in percent.

Thus percent yield of aspirin = 16.87 %.