Question

Assertion (A) $K, Rb $ and $Cs$ form superoxides.
Reason (R) The stability of the superoxides increases from '$K$' to '$Cs$' due to decrease in lattice energy.
The correct answer is

• A. Both (A) and (R) are true and (R) is the correct explanation of (A)
• B. Both (A) and (R) are true but (R) is not the correct explanation of (A)
• C. (A) is true but (R) is not true
• D. (A) is not true but (R) is true

Answer 1

Answer: (C)

Superoxides are the species having an $O-O$ bond and $O$ in an oxidation state of $-\frac{1}{2}$ (superoxide ion is $O _{2}^{-}$).
Usually these are formed by active metals such as $KO _{2}, RbO _{2}$ and $CsO _{2}$.
For the salts of larger anions (like $O _{2}^{-}$), lattice energy increases in a group.
Since, lattice energy is the driving force for the formation of an ionic compound and its stability, the stability of the superoxides from '$K$' to '$Cs$' also increases.