Question

Arrange the following alkali metal carbonates in increasing order of their thermal stability:

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

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

Answer 1

The correct option is A $L{i}_{2}C{O}_3<N{a}_{2}C{O}_3<K_{2}C{O}_3<R{b}_{2}C{O}_3<C{s}_{2}C{O}_3$

Thermal stability is a stability of a molecule at high temperature. A molecule with more stability has more resistance to decomposition at high temperatures.

As we move from top to bottom in a group, the thermal stability increases.

Thermal stability decreases from Li to Cs.

So, the correct order of thermal stability will be-

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

Hence, option $\left(A\right)$ is correct.