Question

Aspirin can be made in the laboratory by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation is

C4H6O3+C7H6O3?C9H8O4+C2H4O2
In a laboratory synthesis, a student begins with 2.90mL of acetic anhydride (density=1.08g/ml) and 1.28g of salicylic acid. Once the reaction is complete, the student collects 1.23g of aspirin.
Determine the limiting reactant for the reaction?
Determine the theoretical yield of aspirin for the reaction?
Determine the percent yield of aspirin for the reaction.

Answer 1

Salicylic Acid is the limiting reagent

Theoretical yield Aspirin: 1.62 g

Percent yield: 76 %

Step-by-step explanation:

The balanced chemical reaction is

C4H6O3+C7H6O3 ⇒ C9H8O4+C2H4O2

Therefore is a 1:1 reaction. This information along the molecular weights of C4H6O3 (MW: 102.9 g/mol), C7H6O3 (MW: 138.1 g/mol) and C9H8O4 (MW: 180.2 g/mol) is sufficient to answer the question once we have converted the mass to mol for the reactants.

mass C2H4O2 = d x v = 2.90 mL x 1.08 g/mL = 3.13 g

# mol C2H4O2 = 3.13 g/102.9 g/mol = 0.030

# mol C7H6O3 = 1.28 g/138.1 g/mol = 0.009

Therefore C7H6O3 is the limiting reagent since it reacts 1: 1 with C2H4O2

Calculation of theoretical yield:

0.009 mol C7H6O3 x 1 mol C9H8O4 / 1mol C7H6O3 = 0.009 mol C9H8O4

Now we convert mol of aspirin :

0.009 mol C9H8O4 x 180.2 g/mol = 1.62 g ( 100 % yield)

Percent yield:

1.23 g collected/ 1.62 g x 100 = 76 %