Assertion (A) : Decomposition reactions are generally endothermic reactions.

Reason (R) : Decomposition of organic matter into compost is an exothermic process.

options

1. (A) and (R) are true and (R) is the reason for (A).
2. (A) and (R) are true and (R) is not the reason for (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.

(A) and (R) are true and (R) is not the reason for (A).

Reason —

• Assertion (A) is true because most decomposition reactions require an external supply of energy—such as heat, light, or electricity—to break down a compound into simpler substances. In these reactions, the chemical bonds within the compound absorb energy to split apart. For example, when calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide. Similarly, in the electrolysis of water, electrical energy is needed to decompose water into hydrogen and oxygen gases. Thus, decomposition reactions are generally endothermic in nature.

• Reason (R) is true because the decomposition of organic matter into compost involves the action of microorganisms such as bacteria and fungi, which break down complex organic substances like plant and animal waste into simpler compounds. During this biological breakdown, a large amount of heat energy is released into the surroundings. That is why compost heaps often feel warm inside.

Hence, (A) and (R) are true and (R) is not the reason for (A).