Percentage yield

An actual yield is the mass of a product actually obtained from the reaction. It is usually less than the theoretical yield. The reasons for this include:

  • incomplete reactions, in which some of the reactants do not react to form the product
  • practical losses during the experiment, such as during pouring or filtering
  • side reactions (unwanted reactions that compete with the desired reaction)

Calculating percentage yield

The percentage yield is calculated using this equation:

percentage\ yield\ =\ \frac{actual\ yield}{theoretical\ yield}\ \times\ 100

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The percentage yield can vary from 100% (no product has been lost) to 0% (no product has been made)

Worked example

Copper oxide reacts with sulfuric acid to make copper sulfate and water. In an experiment, 1.6 g of dry copper sulfate crystals are made. If the theoretical yield is 2.0 g, calculate the percentage yield of copper sulfate.

actual yield = 1.6 g

percentage\ yield\ =\ \frac{1.6}{2.0}\ \times\ 100

percentage yield = 80%

Question

In an experiment, the theoretical yield is 3.2 g but the actual yield is only 2.4 g. Calculate the percentage yield.

percentage\ yield\ =\ \frac{2.4}{3.2}\ \times\ 100

percentage yield = 75%