What is the percentage yield and how do you calculate it?

• A. Percentage yield = theoretical yield / actual yield × 100
• B. Percentage yield = actual yield / theoretical yield × 100
• C. Percentage yield = (actual yield − theoretical yield) × 100
• D. Percentage yield = actual yield × theoretical yield ÷ 100

Answer: (B)

Percentage yield shows how efficient a reaction is by comparing what you actually obtained with the maximum amount that could be produced. It is calculated by dividing the actual yield by the theoretical yield and multiplying by 100. The actual yield is what you collected from the experiment; the theoretical yield is the amount predicted by the balanced equation if everything goes perfectly. To find the theoretical yield you use stoichiometry from the balanced equation, often considering the limiting reactant. For example, if the theoretical yield is 12 g but you only obtain 9 g, the percentage yield is (9/12)×100 = 75%. Make sure both yields are in the same units. Other formulas would not correctly represent the proportion of product obtained relative to the maximum possible.