Percentage Yield and Atom Economy [H]

This lesson covers percentage yield and atom economy as required by the AQA GCSE Chemistry specification (4.3.2). This is Higher Tier only content. You need to understand why actual yield is often less than theoretical yield, be able to calculate percentage yield and atom economy, and explain why these measures are important in industrial chemistry.

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Theoretical Yield and Actual Yield

The theoretical yield is the maximum mass of product that could be formed in a chemical reaction, calculated from the balanced equation and the mass of the limiting reactant. The actual yield is the mass of product that is actually obtained when the reaction is carried out in practice.

Term	Definition
Theoretical yield	The maximum mass of product calculated from the balanced equation
Actual yield	The mass of product actually obtained from the experiment
Percentage yield	The actual yield expressed as a percentage of the theoretical yield

The actual yield is always less than or equal to the theoretical yield. It can never exceed it.