You and a friend work at a major pharmaceutical company as medicinal chemists. Y
ID: 922526 • Letter: Y
Question
You and a friend work at a major pharmaceutical company as medicinal chemists. You have a bet as to whom is the better chemist and decide to have a chemical cook-off. The challenge is to perform the synthesis of a common medicine and the one with higher yield wins. The medicine chosen is Aspirin.
Aspirin, C9H8O4, is produced from salicylic acid, C7H6O3, and acetic anhydride, C4H6O3:
C7H6O3 + C4H6O3 C9H8O4 + HC2H3O2
Both of you will start with 225.0 kg of salicylic acid and 175.0 kg of acetic anhydride.
What is the limiting reactant?
What is the theoretical yield of Aspirin assuming the quantities used above?
Your friend achieved a percent yield of 85%. In order to win the challenge, you need to have a percent yield of at least 86%. What mass of Aspirin should you make in order to win?
Explanation / Answer
C7H6O3 + C4H6O3 C9H8O4 + HC2H3O2
Molecular weight of salicylic acid (C7H6O3)= 7*12+6+48= 138
Molecular weight of Acetic anhydride C4H6O3= 4*12+6+48= 102
Moles of salicylic acid in 225 Kg= 225/138= 1.63 kg moles
Moles of acetic anhydride in 175 kg =175/102 =1.72
Stoichiometric ratio = 1:1 (
Actual ratio = 1.63 :1.72 = 1: 1.72/1.63= 1:1.055
Excess is acetic anhydride
Limiting reactant is salicylic acid
Theoretical yield is governed by the moles of limiting reactant= 1.63 kg moles
Moles of Aspirin formed= 1.63 Kg moles
Molecular weight of Aspirin= 9*12+8+4*16= 180
Mass of Aspirin produced= 1.63*180= 293.4 Kg
Since yield to be achieved = 86%
85% yield= 293.4*0.85= 249.39 kg of Aspirin
Yiled to be obtained =86%
Hence aspirin to be produced= 293.4*0.86= 252.3kg
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