Percentage Yield and Atom Economy

This lesson covers percentage yield and atom economy as required by the Edexcel GCSE Combined Science specification (1SC0). You will learn how to calculate both values and understand why they are important in industrial chemistry.

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Theoretical Yield vs Actual Yield

Term	Definition
Theoretical yield	The maximum mass of product calculated from the balanced equation and the amounts of reactants used.
Actual yield	The mass of product actually obtained from the experiment.

The actual yield is almost always less than the theoretical yield.

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Percentage Yield

Percentage yield compares the actual yield to the theoretical yield:

$\text{percentage yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$percentage yield=theoretical yieldactual yield​×100%

• Percentage yield is always between 0% and 100%.
• A yield of 100% means every atom of reactant was converted to the desired product — this is almost never achieved in practice.

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Worked Examples — Percentage Yield

Example 1

Question: The theoretical yield of copper sulfate from a reaction is 16.0 g. A student obtains 12.0 g. What is the percentage yield?

$\text{percentage yield} = \frac{12.0}{16.0} \times 100 = 75.0\%$percentage yield=16.012.0​×100=75.0%

Example 2