AP EAPCET 07-Jul-2022 Shift 2 Paper

Alkali metals are strong reducing agents because after the removal of the only valence electron $(n s^{1})$ they can gain the electronic configuration of noble gases $(n-1) p^{6}$, that is more stable electronic configuration. $\mathrm{KO}_{2}$ is paramagnetic oxide due to the presence of 1 unpaired electrons. The number of electrons present is 17 where the sixteen electrons are from two oxygen atoms and one from the negative charge $(\mathrm{O}_{2}^{-})$. Its molecular orbital configuration can be written as $\sigma 1s^{2} \sigma^{\times} 1s^{2} \sigma 2s^{2} \sigma^{\times} 2s^{2} \sigma 2p_{z}^{2} \pi 2p_{x}^{2} = \pi 2p_{y}^{2} \pi \times 2p_{x}^{2}$$= \pi^{\times} 2p_{y}^{1} \sigma \times 2p_{z}^{0}.$ So, statement (B) is wrong. The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes. $\mathrm{Li}^{+} > \mathrm{Na}^{+} > \mathrm{K}^{+} > \mathrm{Rb}^{+}$ $\mathrm{Li}^{+}$has maximum degree of hydration and for this reason, lithium salts are mostly hydrated, e.g. $\mathrm{LiCl} \cdot 2 \mathrm{H}_{2}\mathrm{O}$.