Question

Given:
Weight of Salicylic Acid: 1.5092g
Volume of acetic anhydride: 5.00mL
Weight of Acetic Anhydride: 5.4g (density, p = 1.08g/mL)

Molecular Weight of Salicylic Acid = 138.12g/mol // Acetic Anhydride 102.09g/mol
Molecular Weight of acetylsalicylic acid, ASA: 180.157g/mol

Weight of acetylsalicylic acid product (in experiment): 0.50g

Determine the limiting reagent in the reaction: (CH3CO)2O + C7H6O3 -> CH3COOH + C9H8O4
And Calculate the theoretical yield and the actual percent yield of the asprin.

Answer 1

(CH3CO)2O + C7H6O3 -> CH3COOH + C9H8O4

1 equivalent of salicylic acid reacts with 1 equivalent of acetic anhydride to produce 1 eq of acetylsalicylic ester and 1 eq of acetic acid.

moles of salicylic acid = 1.5092 g / 138.12 g/mol => 0.0109267 molesa

moles of acetic anhydride = 5.4 g / 102.09 g/mol => 0.05298 moles

so salicylic acid is the limitting reagent ( reagent that is insufficient) and acetic anhydride is excess reagent.

moles of product = moles of limitting reagent = 0.0109267 moles

Therotical mass of product = 0.0109267 moles * 180.157 g /moles => 1.968 g

% Yield = ( 0.5 g / 1.968 g) * 100 => 25.4 %