Name the three types of decomposition reactions based on the energy used to bring them about, and give one example reaction for each.
Generated by claude-sonnet-4-6 · 2026-06-26 00:54 · grounding rag
Model Answer
The three types of decomposition reactions based on energy used are:
- Thermal decomposition (heat energy):
$$2\text{FeSO}_4(s) \xrightarrow{\Delta} \text{Fe}_2\text{O}_3(s) + \text{SO}_2(g) + \text{SO}_3(g)$$
- Electrolytic decomposition (electrical energy):
$$2\text{H}_2\text{O}(l) \xrightarrow{\text{electricity}} 2\text{H}_2(g) + \text{O}_2(g)$$
- Photolytic decomposition (light energy):
$$2\text{AgCl}(s) \xrightarrow{\text{sunlight}} 2\text{Ag}(s) + \text{Cl}_2(g)$$
Source: Chapter 1, Section 1.2 Types of Chemical Reactions
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Explanation
- Examiners expect all three names correctly stated with the type of energy clearly identified — this earns 1 mark each.
- Each reaction must be balanced and include state symbols where possible for full credit.
- These three examples (FeSO₄, electrolysis of water, AgCl) are the standard textbook examples — use them exactly.
- The key term for light-based decomposition is photolytic (or photodecomposition); writing just "light decomposition" may lose a mark.