Using Moles to Balance Equations (AQA GCSE Chemistry): Revision Notes

You can also use moles to help balance chemical equations. This involves converting the mass of each substance in the reaction to moles, finding the simplest ratio of moles, and then using that ratio to balance the equation.

Worked Example:

• Imagine you are making ammonia (NH₃) by reacting nitrogen (N₂) with hydrogen (H₂). You start with 5.6 g of nitrogen and 1.2 g of hydrogen, and you end up with 6.8 g of ammonia. Here's how you would write the balanced equation:

1. Calculate the moles:

• Moles of nitrogen:

• Moles of hydrogen:

• Moles of ammonia:

2. Simplify the ratio by dividing all the mole amounts by the smallest one (0.2):

• Nitrogen:

• Hydrogen:

• Ammonia:

3. Write the balanced equation: