GK QUESTION#3353
Match the decomposition reactions with the reaction-type labels.
Read each row across both columns.
| Reaction | Type |
|---|---|
| A. Decomposition of H₂O | 1. Redox reaction |
| B. Decomposition of NaH | 2. Redox reaction |
| C. Decomposition of KClO₃ | 3. Redox reaction |
| D. Decomposition of CaCO₃ | 4. Non-redox reaction |
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Answer
A. A-1, B-2, C-3, D-4
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Explanation
Electrolysis of water, decomposition of sodium hydride to its elements, and decomposition of potassium chlorate to potassium chloride and oxygen all change oxidation numbers and are redox reactions. In CaCO₃→CaO+CO₂, Ca remains +2, C remains +4 and O remains −2, so it is non-redox. Labels 1, 2 and 3 all mean redox; only option A pairs D with the non-redox label 4.