Question

Which of the following is/are not correctly matched?

• A. Basic strength of oxides: $C{s}_{2}O$ < $R{b}_{2}O$ < $K_{2}O$ < $N{a}_{2}O$ < $L{i}_{2}O$
• B. Stability of peroxides: $N{a}_2{O}_2$ < $K_2{O}_2$ < $R{b}_2{O}_2$ < $C{s}_2{O}_2$
• C. Stability of bicarbonates: $LiHC{O}_3$ < $NaHC{O}_3$ < $KHC{O}_3$ < $RbHC{O}_3$ < $CsHC{O}_3$
• D. Melting point: $NaF$ < $NaCl$ < $NaBr$ < $NaI$

Answer 1

Answer: (A), (D)

The correct options are
A Basic strength of oxides: $C{s}_{2}O$ < $R{b}_{2}O$ < $K_{2}O$ < $N{a}_{2}O$ < $L{i}_{2}O$
D Melting point: $NaF$ < $NaCl$ < $NaBr$ < $NaI$

Basic strength of the oxides increase in the order $L{i}_{2}O$ <$N{a}_{2}O$ < $K_{2}O$ < $R{b}_{2}O$ < $C{s}_{2}O$. The increase in basic strength is due to the decrease in ionisation energy and increase in electropositive character.
The melting points of the halides decrease in the order $NaF$ > $NaCl$ > $NaBr$ > $NaI$, as the size of the halide ion increases. The decrease in melting point is due to increase in the covalent character with increase in the size of anion according to Fajan's rule.

Option A and D are correct.