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Oxidation number of potassium in K2O, K2O2 and KO2, respectively, is:

1. +1, +2 and +4
2. +2, +1 and +1/2
3. +1, +1 and +1
4. +1, +4 and +2

Correct answer: +1, +1 and +1

Solution

Potassium has oxidation number +1 in K2O, K2O2 (peroxide) and KO2 (superoxide); only oxygen varies (-2, -1, -1/2). So +1, +1, +1.

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