Balancing Equations

Part of the Stoichiometry section of Coddy's Chemistry journey. Lesson 18 of 41.

Atoms are not made or destroyed in a reaction, only rearranged: the law of conservation of mass. The products weigh as much as the reactants.

Two balances with the same beaker, both reading 152.40 g, before and after a reaction inside it

The reading does not change

So each kind of atom must be counted the same on both sides. H₂ + O₂ → H₂O has 2 O on the left but 1 on the right. Add coefficients:

2H₂ + O₂ → 2H₂O

Change coefficients only, never the small numbers: H₂O₂ is another substance. Use the lowest whole numbers; a 1 is not written.

Challenge

Aluminum metal reacts with oxygen to form a thin layer of aluminum oxide, Al₂O₃, that protects it. Balance the equation.

Try it yourself

Equation balancerBalance the equation

AlO₂Al₂O₃

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Stoichiometry

1The Mole

4Equations and Mole Ratios

2Gases

5Limiting Reactant

3Solutions

6Practice Problems