PROBLEM 91P
Aspirin can be made in the laboratory by reacting acetic anhydride (C4HgO3) with salicylic acid (C7H6O3) to form aspirin (C9HgO4) and acetic acid (C2H4O2). The balanced equation is:
C4H6O3 + C7H6O3 → C9H8O4 + C2H4O2
ln a laboratory synthesis, a student begins with 5.00 mL of acetic anhydride (density = 1.08 g/mL) and 2.08 g of salicylic acid. Once the reaction is complete, the student collects 2.01 g of aspirin. Determine the limiting reactant, theoretical yield of aspirin, and percent yield for the reaction.
Solution 91P
Step 1:
C4H6O3 + C7H6O3 → C9H8O4 + C2H4O2
Given that initial volume of acetic anhydride is 5.00 mL and density is 1.08 g/mL
Mass= density volume=5.00 mL
1.08 g/mL=5.4 g
Number of moles of C4H6O3 = Given mass/Molecular mass
Molecular mass of C4H6O3=102g/mol
Thus number of moles of C4H6O3==0.052 moles
Step 2:
Given that mass of C7H6O3 is 2.08 g
Number of moles of C7H6O3 =Given mass/Molecular mass
Molecular mass of C7H6O3=138g/mol
Thus number of moles of C7H6O3==0.015 moles
Step 3:
From the equation it is clear that 1 mole of C4H6O3 combines with 1 mole of C7H6O3 to give 1 mole each of aspirin and acetic acid.Thus we can say that the ratio in which both the reactants should be present is 1:1.Since lesser amount (less than 0.052)of C7H6O3 is present ,it should be the limiting reagent.
