Generated by claude-sonnet-4-6 · 2026-06-14 10:31 · grounding rag
Model Answer
(a)(i) A reaction in which a single reactant breaks down to give two or more products is called a decomposition reaction.
- Heat: $2\text{FeSO}_4 \xrightarrow{\Delta} \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3$
- Light: $2\text{AgCl} \xrightarrow{\text{sunlight}} 2\text{Ag} + \text{Cl}_2$
- Electricity: $2\text{H}_2\text{O} \xrightarrow{\text{electric current}} 2\text{H}_2 + \text{O}_2$
(a)(ii) During decomposition of vegetable matter, microorganisms break down complex organic substances. This process releases heat energy into the surroundings, making it an exothermic reaction.
Source: Chapter 1, Chemical Reactions and Equations
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Explanation
- The definition must include: one reactant → two or more products.
- Give one equation each for heat, light, and electricity — all three are required.
- For part (ii), the key point is that energy (heat) is released during the process, which is the defining characteristic of an exothermic reaction. Examiners look for the word "released" or "given out."