InterviewSolution
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InterviewSolution
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The stability of peroxide and superoxide of alkali metals increase as we go down to group. Explain giving reason. |
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Answer» The stability of peroxide or superoxide increases as the size of metal ion increases i.e., `KO_(2) lt RbO_(2) lt CsO_(2)` ltbr. The reacivity of alkali metals towards oxygen to form different oxides is due to strong positive field around each alkali metal cation. `Li^(+)` is the smallest. It does not allow `O^(2-)` ion to react with `O_(2)` further. `Na^(+)` is larger than `Li`, its positive field is weaker than `Li^(+)`. It cannot prevent then conversion of `O^(2-)` into `O_(2)^(2-)`. The largest `K^(+),Rb^(+)` and `Cs^(+)` ions permit `O_(2)^(2-)` ion to react with `O_(2)` formign superoxide ion `O_(2)^(-)`. `underset("Oxide")(O_(2)^(2-))overset((1)/(2)O_(2))rarrunderset("Peroxide")(O^(2-))overset(O_(2))rarr underset("Superoxide")(2O_(2)^(-))` Futhermore, increased stability of the peroxide or superoxide with increase in the size of metal ion is due to the stabilisation of large anion by larger cations through lattice energy effect. |
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