# 4.3.3.1

4.3.3.1 Percentage yield

## Content

• Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product because:
• the reaction may not go to completion because it is reversible
• some of the product may be lost when it is separated from the reaction mixture
• some of the reactants may react in ways different to the expected reaction.
• The amount of a product obtained is known as the yield. When compared with the maximum theoretical amount as a percentage, it is called the percentage yield.

Students should be able to:

• calculate the percentage yield of a product from the actual yield of a reaction
• (HT only) calculate the theoretical mass of a product from a given mass of reactant and the balanced equation for the reaction

WS 4.2 Recognise the importance of scientific quantities and understand how they are determined.

WS 4.6 Use an appropriate number of significant figures in calculation.

MS 1a - Recognise and use expressions in decimal form

MS 1c Use ratios, fractions and percentages

MS 2a Use an appropriate number of significant figures

MS 3b Change the subject of an equation