Question

In the reaction of 1.23 g of salicylic acid, molar mass 138.12 g/mol, with 2.85 g of acetic anhydride, molar mass 102.10 g/mol, a student obtained 1.39 g of acetylsalicylic acid, molar mass 180.17 g/mol. What is the percent yield?
I found that salicylic acid was the limiting reactant so do I just find the mass from there?

Answer 1

The balanced reaction would be written as:
C7H6O3 + C4H6O3--->C9H8O4 + HC2H3O2
To determine the percent yield, we need to first determine the theoretical yield if the reaction were to proceed completely. Then, we divide the actual yield that is given to the theoretical yield times 100 percent. The limiting reactant from the reaction would be salicylic acid. We do as follows: 

Theoretical yield: 1.23 g C7H6O3 ( 1 mol / 138.21 g ) ( 1 mol C9H8O4 / 1 mol C7H6O3 ) ( 180.157 g / mol ) = 1.60 g C9H8O4 should be produced

Percent yield = 1.39 / 1.60 x 100 = 86.88%

Thus, only 86.88% of the theoretical C9H8O4 is being produced.