CBSE 2025 · Region 1 · Set 1 · Q17 · 1 mark
Assertion (A) : Decomposition reactions are generally endothermic reactions.
Reason (R) : Decomposition of organic matter into compost is an exothermic process.
Official answer
From CBSE’s own marking scheme for this paper.
(B)
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Chemical Reactions and EquationsCombination and Decomposition ReactionsAnalyseassertion_reasonmedium
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.