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Assertion (A): When KMnO4 acts as an oxidising agent in alkaline medium, its equivalent mass equals one-third of its molecular mass. Reason (R): The oxidation number of Mn in KMnO4 is +7. Choose the correct option.

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is not the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false and (R) is true

Correct answer: Both (A) and (R) are true but (R) is not the correct explanation of (A)

Solution

In alkaline medium Mn changes +7 to +4 (3 electrons), so equivalent mass = M/3 (A true); R correctly states the +7 state but that alone does not explain the factor of 3, which comes from the 3-electron change.

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