Theoretical and Percent Yield

Question

In an Aspirin preparations, 4.40g of aspirin are obtained from 5.00 g each of salicylic acid and acetic anhydride. Calculate ether theoretical and percent yield of aspirin

Answer 1

You need to consider the balanced chemical equation for the production of aspirin.

salicylic acid + acetic anhydride ==> aspirin + acetic acid

Next, determine which reactant is limiting:

moles salicylic acid = 5.00 g x 1 mole/138 g = 0.0362 moles

moles acetic anhydride = 5.00 g x 1 mole/102 g = 0.0490 moles

Thus, salicylic acid is limiting and will determine moles of aspirin that can form.

Moles or aspirin theoretically formed = 0.0362 moles SA x 1 mole aspirin/mole SA = 0.0362 moles aspirin

Theoretical mass of aspirin = 0.0362 moles x 180 g/mole = 6.52 g

% yield = actual yield/theoretical yield (x100%) = 4.40 g/6.52 g (x100%) = 67.5%