Chemistry: Stoiciometry

Question

A Student used 4.55 grams of salicylic acid, along with acetic anhydride, to prepare aspirin.

C7H6O3 + C4H6O3 -> C9H8O4 + C2H4O2
(salicylic)   (acetic an)  (aspirin)    (acetic acid)

(a)Find the theoretical yield of the aspirin.
(b)Find the percent yield of aspirin if the student prepared 2.45 grams of aspirin. 

Answer 1

molar mass of salicylic acid = 138.1 g/mole

molar mass aspirin = 180.2 g/mole 

moles salicylic acid used = 4.55 g x 1 mole/138.1 g = 0.03294 moles

moles aspirin expected @ 100% yield = 0.03294 moles b/c there is a 1:1 mole ratio between SA and aspirin

grams aspirin expected (Theoretical Yield) =0.03294 moles x 180.2 g/mole = 5.94 g (to 3 significant figures)

% yield = 2.45 g/5.94 g (x100%) = 41.2%