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The main oxides formed on combustion of Li, Na and K in excess of air are, respectively:

1. Li2O2, Na2O2 and KO2
2. Li2O, Na2O2 and KO2
3. Li2O, Na2O and KO2
4. LiO2, Na2O2 and K2O

Correct answer: Li2O, Na2O2 and KO2

Solution

Lithium primarily forms lithium oxide (Li2O) upon combustion, while sodium reacts to form sodium peroxide (Na2O2) due to its ability to stabilize the peroxide ion. Potassium, being more reactive, forms potassium superoxide (KO2) in the presence of excess oxygen.

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