The molar mass of aspirin is 180.16 g/mol. What is the theoretical yield in grams, for the aspirin she theoretically obtained above using 4.02 g of SA?

Question

The molar mass of aspirin is 180.16 g/mol. What is the theoretical yield in grams, for the aspirin she theoretically obtained above using 4.02 g of SA? What is the percent yield?

Answer 1

By SA you mean Salicylic acid

 

First you have to right out the balanced equation...

 

C7H6O3   +     C4H6O3  ----->  C9H8O4 + C2H4O2

 

 

The C9H8O4 is the aspirin.  We know it is at a 1:1 molar ratio with salicylic acid so

 

we Take 4.80 g of SA   *  1 mole SA  / MW of SA which is 138.121.  When we do the calculation we get .034 moles of SA.

 

We know this is a one to one molar ratio to aspirin

 

so we take the .034 moles SA * 1 mole Aspirin/1mole SA * 180.16 g Aspirin/1 mole SA= 6.13 g Aspirin is your theoretical yield

Answer 2

The reaction can be written as :  1 mole SA + 1 mole acetic anhydride ==> 1 mole aspirin

moles of SA started with = 4.02 g x 1 mol/138.1 g = 0.0291 moles

moles of aspirin expected = 0.0291 since you get 1 mole aspirin from 1 moles SA

grams of aspirin expected = 0.0291 moles x 180.16 g/mol = 5.24 grams = theoretical yield

 

One cannot calculate the per cent yield since we don't know the actual yield.  We don't know what the "above" refers to.

But if, for example, she obtained 4.52 grams "above", then you calculate % yield as (100)x 4.52g/5.24g = 86.3%