Question

Calculate the theoretical yield of aspirin to be obtained when 2.0 g of salicylic acid and 5.0 mL of acetic anhydride (density = 1.08 g/mL) are mixed together. What is the limiting reagent?

Answer 1

The theoretical yield is 2.61 grams of aspirin

salicylic acid is the limiting reactant.

Step-by-step explanation:

Step 1: Data given

Mass of salicylic acid = 2.0 grams

Volume of acetic acid = 5.0 mL

Density of acetic acid = 1.08 g/mL

Molar mass of acetic anhydride = 102.09 g/mol

Molar mass of salicylic acid = 138.12 g/mol

Step 2: The balanced equation

C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH

Step 3: Calculate mass of acetic acid

Mass acid acid = density * volume

Mass acetic acid = 1.08 g/mL * 5.0 mL

Mass acetic acid = 5.5 grams

Step 4: Calculate moles salicylic acid

Moles salicylic acid = mass salicylic acid / molar mass salicylic acid

Moles salicylic acid = 2.00 grams / 138.12 g/mol

Moles salicylic acid = 0.0145 moles

Step 5: Calculate moles acetic anhydride

Moles acetic anhydride= 5.5 grams / 102.09 g/mol

Moles acetic anhydride = 0.0538 moles

Step 6: Calculate the limiting reactant

For 1 mol salicylic acid we need 1 mol acetic anhydride to produce 1 mol aspirine.

The limiting reactant is salicylic acid. It will completely be consumed. (0.0145 moles). Acetic anhydride will be in excess. There will react 0.0145 moles . There will remain 0.0538 - 0.0145 = 0.0393 moles

Step 7: Calculate moles aspirine

For 1 mol salicylic acid we need 1 mol acetic anhydride to produce 1 mol aspirine.

For 0.0145 moles salicylic acid, we'll have 0.0145 moles aspirine

Step 8: Calculate mass of aspirin

Mass aspirin = moles aspirin * molar mass aspirin

Mass aspirin = 0.0145 moles * 180.158 g/mol

Mass aspirin = 2.61 grams = Theoretical yield

The theoretical yield is 2.61 grams of aspirin

salicylic acid is the limiting reactant.