To calculate the theoretical yield of aspirin starting with 20 g of salicylic acid, we first need to know the balanced chemical equation for the synthesis of aspirin, which is:
Salicylic Acid + Acetic Anhydride → Aspirin + Acetic Acid
Next, we determine the molar mass of salicylic acid (C7H6O3), which is about 138.12 g/mol. By calculating the number of moles in 20 g of salicylic acid:
Number of moles = mass / molar mass
Number of moles = 20 g / 138.12 g/mol ≈ 0.145 moles
From the balanced equation, we see that 1 mole of salicylic acid produces 1 mole of aspirin. Thus, 0.145 moles of salicylic acid will theoretically produce 0.145 moles of aspirin.
Now, we need to find the theoretical mass of aspirin using its molar mass. The molar mass of aspirin (C9H8O4) is about 180.16 g/mol:
Theoretical yield (g) = number of moles × molar mass
Theoretical yield = 0.145 moles × 180.16 g/mol ≈ 26.10 g
Hence, the theoretical yield of aspirin is approximately 26.10 g.
How to Calculate Percent Yield of Aspirin?
If 1.8 g of aspirin were obtained, we can calculate the percent yield using the formula:
Percent Yield = (actual yield / theoretical yield) × 100%
Substituting the values we have:
Percent Yield = (1.8 g / 26.10 g) × 100% ≈ 6.89%
This means that the percent yield of aspirin obtained in this experiment is approximately 6.89%.