Balancing equations

This lesson covers: 

  1. Ways to show chemical equations
  2. How to balance symbol equations

Chemical equations

Chemical reactions can be represented by word and symbol equations.

Types of equation

  • Word equations - Use the names of reactants and products.
  • Symbol equations - Use chemical formulas and symbols.
  • Balanced symbol equations - Show the number of reactants and products in a reaction.


Examples:

  • Word equation - magnesium + oxygen —> magnesium oxide
  • Symbol equation - Mg + O2​ —> MgO
  • Balanced symbol equation - 2Mg + O2​ —> 2MgO

Balancing symbol equations

To balance a symbol equation follow these steps:

Chemical equation showing magnesium reacting with oxygen to form magnesium oxide

1Write the word equation for the reaction.

2Then add in the chemical formulae to form a symbol equation

Diagram showing an unbalanced symbol equation with magnesium and oxygen reactants forming magnesium oxide products.

3Count the numbers of each type of atom on both sides of the equation.

4This equation is unbalanced as there are more oxygen atoms on the left hand side than the right hand side.

Diagram showing the balancing of a symbol equation with reactants magnesium and oxygen forming products magnesium oxide.

5Pencil in numbers before formulas to try to balance unequal atoms.

6Count the numbers of each type of atom on both sides of the equation.

7This equation is still unbalanced as there are more magnesium atoms on the right hand side than the left hand side.

Diagram showing the balancing of a chemical equation with magnesium and oxygen atoms.

8We repeat the steps 5 and 6 until the numbers of each type of atom are the same on both sides of the arrow.

9This gives us the balanced symbol equation for this chemical reaction.