Question

1.22 g of acetylsalicylic acid was obtained from 2.00 g of salicylic acid by reaction with
excess acetic anhydride. Calculate the percentage yield of acetylsalicylic acid.

Answer 1

The theoretical yield must be estimated to calculate the percentage yield of acetylsalicylic acid.

The molecular weight of acetylsalicylic acid is 180 g/mol.

The molecular weight of salicylic acid is 138 g/mol.

As a result:

Salicylic acid mass / salicylic acid molecular weight = Acetylsalicylic acid mass / acetylsalicylic acid molecular weight

From here:

Acetylsalicylic acid mass = (Salicylic acid mass × acetylsalicylic acid molecular weight) / salicylic acid molecular weight

Acetylsalicylic acid mass = (2 g × 180 g/mol / 138 g/mol) = 2.6 g

As the theoretical yield of acetylsalicylic acid is 2.6 g and the actual yield is 1.22 g, the percentage yield of acetylsalicylic acid is:

% yield = (actual yield / theoretical yield) × 100% = 47%

Answer: 47%