Limiting reactants & stoichiometry (Edexcel GCSE Chemistry & Combined Science)

This lesson describes how the limiting reactant controls the mass of the product formed and explains how to deduce the stoichiometry. The PowerPoint and accompanying worksheet, which is differentiated, have been designed to cover points 1.52 & 1.53 of the Edexcel GCSE Chemistry specification and also covers those points in the Chemistry section of the Combined Science course. Step by step guides are used to go through worked examples so students are able to visualise how to set out their work.

The lesson begins with a fun analogy involving sausages and potatoes so that students can identify that the potatoes limited the sale of food. Alongside this, students will learn the key term excess. Some time is then taken to ensure that students can spot the limiting reactant and the one in excess in actual chemical reactions and method descriptions. Moving forwards, students will be guided through two calculations that involve limiting reactants - those to calculate the theoretical yield and the other to calculate a balanced symbol equation. Other skills involved in these calculations such as calculating the relative formula mass are recalled and a few examples given to ensure they are confident. The question worksheet has been differentiated two ways so that any students who need extra assistance can still access the learning.