Balancing chemical equations

Learn how to balance chemical equations

How do you balance a chemical equation?

In a chemical reaction mass is always conserved. This means that matter is not created nor destroyed.

You cannot turn atoms of lead into atoms of gold in a chemical reaction!

In a reaction the same atoms are simply rearranged as old chemical bonds are broken and new bonds are formed.

The chemicals that react are called the reactants. The new chemicals that are produced are called the products.

Reactants Products

Chemical equations are balanced by placing whole numbers in front of the chemical formulas.

An equation is balanced when the number and type of reactant atoms is the same as the number and type of product atoms.

Note: You do not change the chemical formula of a substance to balance a chemical equation.

Examples of Balanced Chemical Equations

1.  Hydrogen and chlorine   hydrogen chloride

One hydrogen molecule reacts with one chlorine molecule to produce two hydrogen chloride molecules.

Whole numbers are placed in front of the chemical formula (shown in red) to balance an equation.

As in algebra a 1 is not needed so H₂ is written instead of 1H₂ and Cl₂ is written instead of 1Cl₂

Let's check if the atoms are the balanced.

2. Hydrogen + oxygen   water

Let's check if the atoms are the balanced.

3. Hydrogen peroxide   water + oxygen

Two hydrogen peroxide molecules break down to produce two water molecules and one oxygen molecule.

Let's check if the atoms are the balanced.

4. Nitrogen + Hydrogen   ammonia

One nitrogen molecule combines with three hydrogen molecules to produce two ammonia molecules

Let's check if the atoms are the balanced.

5. Methane + oxygen   carbon dioxide + water

One methane molecule combines with two oxygen molecules to produce one carbon dioxide molecule and two water molecules.

Let's check if the atoms are the balanced.

Practice problems - Balancing Equations

See also the balancing equations worksheets