Calculating Salicylic Acid Required for Aspirin Production

[Larrytsai]

Aspirin, C9 H8 O4 (molar mass 180.2g/mol), a drug used to relieve minor aches and pains, is prepared by the following reaction:

C7 H6 O3 (s) + C4 H6 O3 (l) --> C9 H8 O4 (s) + C2 H4 O2 (l)

If you need to prepare 45.0g of aspirin, and yield for the reaction is 85% how many grams of salicylic acid, C7 H6 O3 (molar mass 138.1g/mol) must you use?

i was wondering where to start? like I am really confused with that 85% thing too

 

[symbolipoint]

The description and question mean 45 grams of aspirin is 85 percent of what would result if all of the salicylic acid were to become apirin.

 

[eli64]

(45 g/ theoretical yield) x 100 = 85%

 

[chemisttree]

Divide 45g by 85% (expressed as 0.85) to get the theoretical yield.
Solve for the amount of salicylic acid using the relationship of moles of aspirin produced (theoretical) from salicylate used.
Or, you could ask yourself, "How many moles of salicylate would yield 'X' moles (theoretical yield) of aspirin?"