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AQA GCSE Chemistry Formulae and equations

Formulae and equations

This page covers the following topics:

1. Balancing equations
2. Limiting reactants

A balanced equation is a model of a chemical reaction that shows the formulae of the reactants and the products. In order for an equation to be balanced, the number of atoms must be equal on both sides of the equation.

Balancing equations

The limiting reactant is the first reactant to be used up in a chemical reaction. When the limiting reactant is used up, the reaction stops and no more of the product can be formed. Therefore, the mass of the product is dependent on the mass of the limiting reactant. The left-over reactant is referred to as the reactant in excess.

Limiting reactants

1

14.5 g of ammonia are reacted with 7.2 g of oxygen to produce nitric oxide and water. Which reactant is in excess?

14.5 g of ammonia are reacted with 7.2 g of oxygen to produce nitric oxide and water. Which reactant is in excess?

2

Balance the equation Sβ‚ˆ + Fβ‚‚ β†’ SF₆.

Balance the equation Sβ‚ˆ + Fβ‚‚ β†’ SF₆.

3

2.5 g of zinc are reacted with 9.8 g of hydrogen chloride. Which is the limiting reactant?

2.5 g of zinc are reacted with 9.8 g of hydrogen chloride. Which is the limiting reactant?

4

Which is the limiting reactant in the reaction of 9.6 g of nitrogen with 6 g of hydrogen?

Which is the limiting reactant in the reaction of 9.6 g of nitrogen with 6 g of hydrogen?

5

Balance the equation Nβ‚‚ + Hβ‚‚ β†’ NH₃.

Balance the equation Nβ‚‚ + Hβ‚‚ β†’ NH₃.

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