Calculate the theoretical yield and the percent yield of aspirin. (C9H8O4) (more in description)

Question

Aspirin can be synthesized in the lab by combining salicylic acid (C7H6O3) and acetic anhydride (C4H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation for this reaction is

C7H6O3 + C4H6O3 = C9H8O4 + C2H4O2

A student started with 5.00 mL acetic anhydride (density = 1.08 g/mL) and 2.37 g salicylic acid. The student synthesized 2.54 g of aspirin.

Answer 1

C₇H₆O₃ + C₄H₆O₃ = C₉H₈O₄ + C₂H₄O₂ ... balanced equation

First, let's find the limiting reactant, as that will determine the theoretical yield. An easy way to do this is to find moles of each reactant and divide that by the respective coefficient in the balanced equation.

For C₇H₆O₃: 2.37 g x 1 mol / 138 g = 0.0171 mols (÷1->0.0171)

For C₄H₆O₃: 5.00 ml x 1.08 g / ml x 1 mol / 102 g = 0.0529 mols (÷1->0.0529)

C₇H₆O₃ (salicylic acid) is LIMITING

Theoretical yield = 0.0171 mol C₇H₆O₃ x 1 mol C₉H₈O₄ / mol C₇H₆O₃ x 180 g/mol C₉H₈O₄ = 3.08 g C₉H₈O₄

Percent yield = actual yield / theoretical yield (x100%) = 2.54 g / 3.08 g (x100%) = 82.5% yield