Question

Which of the following is not correctly matched?
1) Basic strength of oxides $\to C{s}_{2}O<R{b}_{2}O<K_{2}O<N{a}_{2}O<L{i}_{2}O$
2) Stability of peroxides $\to N{a}_2{O}_2<K_2{O}_2<R{b}_2{O}_2<C{s}_2{O}_2$
3) Stability of bicarbonates $\to LiHC{O}_3<NaHC{O}_3<KHC{O}_3<RbHC{O}_3<CsHC{O}_3$
4) Melting point $\to NaF<NaCl<NaBr<NaI$

• A. (1) and (4)
• B. (1) and (3)
• C. (1) and (2)
• D. (2) and (3)

Answer 1

The correct option is A (1) and (4)

1) Basic strength of the oxides increases in the order: $L{i}_{2}O<N{a}_{2}O<H_{2}O<R{b}_{2}O<C{s}_{2}O$. The increase in basic strength is due to the increase in the size of the metal down the group.
2) Stability of peroxides increases in the order:
$N{a}_2{O}_2<K_2{O}_2<R{b}_2{O}_2<C{s}_2{O}_2$
The stability of peroxide increases as the size of the metal increases, due to the stabilization of larger anions by larger cations.
3) Stability of bicarbonates increases in the order:
$LiHC{O}_3<NaHC{O}_3<KHC{O}_3<RbHC{O}_3<CsHC{O}_3$
The stability of bicarbonates increases as the size of the metal increases down the group.
4) The melting and boiling point of halides follows the trend: Fluorides > Chlorides > Bromides > Iodides. As the size of anions increase, their tendency to get polarised increases and therefore, their covalent character increase and thus melting point decreases. So the melting points of the halides of sodium decreases in the order: $NaF>NaCl>NaBr>NaI$