Question

Aspirin (acetylsalicylic acid) is prepared by heating salicylic acid, C₇H₆O₃, with acetic anhydride, C₄H₆O₃. The other product is acetic acid C₂H₄O₂; according to the following reaction: C7H₆O₃ + C₄H₆O₃ - C₉H₈O₄ + C₂H₄O₂

What is the theoretical yield (in grams) of aspirin, C₉H₈O₄, when 2.0 g of salicylic acid is heated with 4.0 g of acetic anhydride?
If the experimental yield of aspirin is 2.10 g. What is the percent yield of the reaction?

Answer 1

To determine the theoretical yield of aspirin, calculate the moles of salicylic acid and acetic anhydride, and determine the limiting reactant. Salicylic acid is the limiting reactant, so to calculate the theoretical yield, convert the moles of salicylic acid to grams using the molar mass of aspirin. The percent yield can be calculated by dividing the actual yield by the theoretical yield and multiplying by 100.

Step-by-step explanation:

To determine the theoretical yield of aspirin, we need to calculate the moles of salicylic acid and acetic anhydride, and then determine which reactant is the limiting reactant. The balanced equation tells us that 1 mol of salicylic acid reacts with 1 mol of acetic anhydride to produce 1 mol of aspirin. From the given masses of salicylic acid (2.0 g) and acetic anhydride (4.0 g), we can convert the masses to moles using their respective molar masses. Comparing the moles of salicylic acid and acetic anhydride, we find that salicylic acid is the limiting reactant. Therefore, the theoretical yield of aspirin can be calculated by converting the moles of salicylic acid to grams using the molar mass of aspirin.

Given:

Mass of salicylic acid (C7H6O3) = 2.0 g

Mass of acetic anhydride (C4H6O3) = 4.0 g

Calculations:

Molar mass of salicylic acid = 138.12 g/mol

Molar mass of acetic anhydride = 102.09 g/mol

Moles of salicylic acid = (mass of salicylic acid)/(molar mass of salicylic acid) = 2.0 g / 138.12 g/mol = 0.01445 mol

Moles of acetic anhydride = (mass of acetic anhydride)/(molar mass of acetic anhydride) = 4.0 g / 102.09 g/mol = 0.03921 mol

Based on the balanced equation, the ratio of salicylic acid to aspirin is 1:1. Since we have fewer moles of salicylic acid than acetic anhydride, salicylic acid is the limiting reactant.

The theoretical yield of aspirin = moles of salicylic acid x molar mass of aspirin = 0.01445 mol x 180.16 g/mol = 2.60 g

To calculate the percent yield, we divide the actual yield by the theoretical yield and multiply by 100:

Percent yield = (actual yield / theoretical yield) x 100 = (2.10 g / 2.60 g) x 100 = 80.77%