Salicylic Acid and Acetic Anhydride Reaction Calculation

Calculating the Limiting Reactant

In order to understand what the limiting reactant is, we need to convert the masses of reactants into moles. The molecular masses are:

C7H6O3 = 138 g/mol

C4H6O3 = 100 g/mol

Converting masses into moles:

70 g C7H6O3 x (1 mol / 138 g) = 0.5 mol C7H6O3

80 g C4H6O3 x (1 mol / 100 g) = 0.8 mol C4H6O3

In the reaction, 2 moles of C7H6O3 are necessary to react with 1 mol of C4H6O3. Following this ratio:

0.8 mol C4H6O3 x (2 mol C7H6O3 / 1 mol C4H6O3) = 1.6 mol C7H6O3

We have only 0.5 mol of C7H6O3, meaning we don't have enough salicylic acid. Therefore, salicylic acid (C7H6O3) is the limiting reactant.