Answer:
The percent yield would be 73%
Explanation:
The balanced reaction for the obtention of acetylsalicylic acid (aspirin) is the following:
Salicylic acid + acetic anhydride → acetylsalicylic acid + acetic acid
C₇H₆O₃ + C₄H₆O₃ → C₉H₈O₄ + C₂H₄O₂
According to the reaction, 1 mol of salicylic acid reacts with 1 mol of acetic anhydride to give 1 mol of acetylsalicylic acid (aspirin) and 1 mol of acetic acid.
1 mol aspirin (C₉H₈O₄) = (9 x 12 g/mol) + (8 x 1 g/mol) + (4 x 16 g/mol)
= 180 g
1 mol salicylic acid (C₇H₆O₃) = (7 x 12 g/mol) + (6 x 1 g/mol) + (3 x 16 g/mol)
= 138 g
1 mol acetic anhydride (C₄H₆O₃) = (4 x 12 g/mol) + (6 x 1 g/mol) + (3 x 16 g/mol)
= 102 g
The stoichiometric ratio is = 138 g salicylic acid/102 g acetic anhydride= 1.35
We have:
2.0 g salicylic acid
acetic anhydride = 5.0 mL x 1.08 g/mL = 5.4 g
The reactants ratio is = 2.0 g salicylic acid/5.4 g acetic anhydride = 0.37
0.37 < 1.35 , therefore <em>salicylic acid is the limiting reactant</em>.
Now, we use the amount of salicylic acid to calculate the theoretical amount of aspirin. For this, we know that 1 mol of aspirin (180 g) is obtained from 1 mol of salycilic acid (138 g):
theoretical yield= 180 g aspirin/138 g salycilic acid x 2.0 g salycilic acid = 2.61 g aspirin
actual yield = 1.9 g
Finally, we calculate the yield:
percent yield = actual yield/theoretical yield x 100
= 1.9 g/2.6 g x 100 = 72.8% ≅ 73%
