sblock Elements 2 Question 13
13. The following compounds have been arranged in order of their increasing thermal stabilities. Identify the correct order.
$\mathrm{K}{2} \mathrm{CO}{3}$ (I), $\mathrm{MgCO}{3}$ (II), $\mathrm{CaCO}{3}$ (III), $\mathrm{BeCO}_{3}$ (IV)
(a) I $<$ II $<$ III $<$ IV
(b) IV $<$ II $<$ III $<$ I
(c) IV $<$ II $<$ I $<$ III
(d) II $<$ IV $<$ III $<$ I (1996, 1M)
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Answer:
Correct Answer: 13. (c)
Solution:
- Thermal stability of salts with common anion depends on polarising power of cation. Greater the polarising power, lower be their thermal stability. Hence,
$$ \mathrm{BeCO}{3} \text { (IV) }<\mathrm{MgCO}{3} \text { (II) }<\mathrm{CaCO}{3} \text { (III) }<\mathrm{K}{2} \mathrm{CO}_{3} \text { (I) } $$
