Question

Which of the following is(are) not correctly matched?

(1) Basic strength of oxides: $C{s}_{2}O<R{b}_{2}O<K_{2}O<N{a}_{2}O<L{i}_{2}O$

(2) Stability of peroxides: $N{a}_2{O}_2<K_2{O}_2<R{b}_2{O}_2<C{s}_2{O}_2$

(3) Stability of bicarbonates: $LiHC{O}_3<NaHC{O}_3<KHC{O}_3<RbHC{O}_3<CsHC{O}_3$

(4) Melting point: $NaF<NaCl<NaBr<NaI$

• A. $\left(1\right)$ and $\left(4\right)$
• B. $\left(1\right)$ and $\left(3\right)$
• C. $\left(1\right)$ and $\left(2\right)$
• D. $\left(2\right)$ and $\left(3\right)$

Answer 1

Answer: (D)

$\left(2\right)$ and $\left(3\right)$

1) Basic strength increases down the group.

$C{s}_{2}O>R{b}_{2}O>K_{2}O>N{a}_{2}O>L{i}_{2}O$

2) The stability of peroxide or superoxide increases as the size of the alkali metal increases. This is due to the stabilisation of large anions by large cations through lattice energy effects.

So, the given order is correct.

3) Small and highly charged metal ions possess more polarizing power and hence facilitates the decomposition of bicarbonate ion into carbonate, carbon dioxide and water. This means the stability of bicarbonates increases as we go down the group.

$2HC{O}_3^{-}\to C{O}_3^{2-}+C{O}_2+H_{2}O$ (on heating)

4) Lattice Energy $\propto \frac{1}{r_{+}+r_{-}}$

More is lattice energy, more is the melting point.

$\therefore NaF>NaCl>NaBr>NaI$

Hence, the correct option is $\text{D}$