Question

Aspirin (C₉H₈O₄) is produced by the reaction of salicylic acid (C₇H₆O₃.M = 138.1 g/mol) and acetic anhydride (C₄H₆O₃.M = 102.1 g/mol):

C₇H₆O₃(s) + C₄H₆O₃(l) --> C₉H₈O₄(s) + C₂H₄O₂(l)

Answer 1

First, determine which reactant is the rate limiting one by seeing how many moles would be produced of product (C9H8O4) if 100% of the reactants were used.

For C7H6O3: 3.03 g C7H6O3/(138.1 g/mol) = 0.0219 mol
For C4H6O3: 4.01 g/(102.1 g/mol) = 0.0393 mol

Complete reaction of C7H6O3 would yield fewer moles, so it must be the rate limiting reactant.

Now calculate how many moles of C9H8O4 2.04 g is:
2.04 g C9H8O4/(180.2 g/mol) = 0.01132 mol C9H8O4

For percent yield:
(0.01132 mol actual yield/0.0219 mol theoretical yield) * 100 = 51.68%