JEE Main · 2022 · 24 Jun 2022 · Shift 1 · s-Block Elements

Lithium shows a diagonal relationship with magnesium, and both $\mathrm{LiCl}$ and $\mathrm{MgC}{\mathrm{l}}_2$ are appreciably covalent, which is why each dissolves in a covalent solvent like ethanol, so the first statement holds. Lithium and magnesium are both too small and too strongly polarising to stabilise the bulky superoxide ion, so on reaction with excess oxygen they give only normal oxides rather than superoxides, which makes the superoxide statement false. Among the alkali metal fluorides $\mathrm{LiF}$ is the odd one out: the very small fluoride ion paired with the very small lithium ion produces an exceptionally high lattice energy that water cannot overcome, so $\mathrm{LiF}$ is indeed the least soluble of them and that statement is correct. Finally $\mathrm{L}{\mathrm{i}}_2\mathrm{O}$ is actually the least soluble of the alkali metal oxides, not the most soluble, so the last statement is false. Only the claim about the ethanol solubility of the chlorides and the claim about the low water solubility of $\mathrm{LiF}$ survive scrutiny.