Question

The correct increasing order of melting point of alkali metal carbonates is:

• A. $C{s}_{2}C{O}_3<N{a}_{2}C{O}_3<K_{2}C{O}_3<R{b}_{2}C{O}_3<L{i}_{2}C{O}_3$
• B. $L{i}_{2}C{O}_3<N{a}_{2}C{O}_3<K_{2}C{O}_3<R{b}_{2}C{O}_3<C{s}_{2}C{O}_3$
• C. $L{i}_{2}C{O}_3<R{b}_{2}C{O}_3<K_{2}C{O}_3<N{a}_{2}C{O}_3<C{s}_{2}C{O}_3$
• D. None of these

Answer 1

Answer: (B)

$L{i}_{2}C{O}_3<N{a}_{2}C{O}_3<K_{2}C{O}_3<R{b}_{2}C{O}_3<C{s}_{2}C{O}_3$

The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point, the solid and liquid phases exist in equilibrium.

The melting point of carbonates of a particular group increases due to an increase in atomic size. This increases the Van der Waal attraction, which requires more heat to melt.

Li, Na, K, Rb, Cs are IA group elements, the melting point increases from Li to Cs.
The correct order of melting point of carbonates of IA group elements is:

$L{i}_{2}C{O}_3<N{a}_{2}C{O}_3<K_{2}C{O}_3<R{b}_{2}C{O}_3<C{s}_{2}C{O}_3$

Hence, option (B) is correct.