# Propane (C₃H₈) is a hydrocarbon used as a fuel in camping stoves. When propane burns completely in oxygen, the products are carbon dioxide and water. The balanced equation for this reaction is: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. Explain why the total mass of carbon dioxide and water produced is always equal to the total mass of propane and oxygen that reacted.

> WJEC A-Level Chemistry (Wales) — 3.2 Hydrocarbons · Explain · 5 marks

> Propane (C₃H₈) is a hydrocarbon fuel. When it burns completely in oxygen, carbon dioxide and water are the only products. The balanced equation for this reaction is: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

## Mark scheme (5 marks)

1. States the law of conservation of mass
2. No atoms are lost or made / created or destroyed during a chemical reaction
3. The same atoms are present on both sides of the equation / in the reactants and products
4. Therefore the mass of the products equals the mass of the reactants
5. Links to the balanced equation: the balancing numbers show atoms of each element are equal on both sides, e.g. 3 carbon atoms on each side / 8 hydrogen atoms on each side / 10 oxygen atoms on each side

## Key terms

- [products](https://www.gradenine.co.uk/glossary/products)
- [balanced equation](https://www.gradenine.co.uk/glossary/balanced-equation)

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- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/propane-c-h-is-a-hydrocarbon-used-0b925923) · Published by Druglandscape Ltd.