Consider the reaction between salicylic acid and acetic anhydride:
(CH3CO)2O(l) + HOC6H4COOH(s) → CH3CO2C6H4CO2H(s) + CH3COOH(aq)
acetic anhydride salicylic acid acetylsalicylic acid acetic acid
When 0.8012g of salicylic acid reacts with 5mL of acetic anhydride, 0.754g of aspirin (acetylsalicylic
acid) are collected. Assuming the salicylic acid is the limiting reactant calculate the theoretical yield of
aspirin (acetylsalicylic acid) and percent yield.
The number of moles of salicylic acid is calculated as shown below where m is the mass and M is the molar mass of salicylic acid. The number of moles of salicylic acid is 0.0058 mol.
According to the chemical equation, one mole of aspirin is produced when one mole of salicylic acid involves in the reaction. So, 0.0058 mol of aspirin is produced from 0.0058 mol of salicylic acid (when considered as limiting reagent). The mass of 0.0058 mol of aspirin is calculated as shown below where M is the molar mass of aspirin. The mass of 0.0058 mol of aspirin (or theoretical yield of aspirin) is 1.045 g.
The percentage yield, Y%, is calculated as shown below where 0.754 g is the observed yield and 1.045 g is the theoretical yield. The percentage yield, Y%, is 71.29 %.