JEE Main · 2023 · 24 Jan 2023 · Shift 2 · s-Block Elements

The reduction potentials ${\mathrm{M}}^{+}|M$ do run as $\mathrm{Na}>\mathrm{Rb}>\mathrm{Li}$ when read with sign, sodium being the least negative and lithium the most negative of the three, so that statement stands. Caesium iodide pairs a large cation with a large anion and its small hydration enthalpy leaves it only sparingly soluble, so the claim of high solubility fails. Lithium carbonate is the least thermally stable alkali metal carbonate and decomposes on heating, so the stability claim fails. A metal in liquid ammonia is blue and paramagnetic only while dilute; concentrated solutions turn bronze and become diamagnetic, so the statement tied to concentrated ammonia fails. Every alkali metal hydride is an ionic solid of ${\mathrm{M}}^{+}$ and ${\mathrm{H}}^{-}$, so that holds. The correct statements are the first and the last.