Hydrogen and oxygen combine to form water vapour.
Name and state the law illustrated by this problem.

Explanation

To solve the question, "Hydrogen and oxygen combine to form water vapour. Name and state the law illustrated by this problem," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants and Product**:
- The reactants are hydrogen (H₂) and oxygen (O₂).
- The product formed is water vapour (H₂O).

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