Chemical And Ionic Equilibrium Result Question 18
18. Identify the correct order of solubility of $\mathrm{Na} _2 \mathrm{~S}, \mathrm{CuS}$ and $\mathrm{ZnS}$ in aqueous medium.
(2002)
(a) $\mathrm{CuS}>\mathrm{ZnS}>\mathrm{Na} _2 \mathrm{~S}$
(b) $\mathrm{ZnS}>\mathrm{Na} _2 \mathrm{~S}>\mathrm{CuS}$
(c) $\mathrm{Na} _2 \mathrm{~S}>\mathrm{CuS}>\mathrm{ZnS}$
(d) $\mathrm{Na} _2 \mathrm{~S}>\mathrm{ZnS}>\mathrm{CuS}$
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Answer:
Correct Answer: 18. ( d )
Solution:
- Alkali metal salts are usually more soluble than the salts of transition metals. Also, $\mathrm{CuS}$ is less soluble than $\mathrm{ZnS}$ because of $3 d^9$ configuration of $\mathrm{Cu}^{2+}$. Therefore, solubility order is
$\mathrm{Na} _2 \mathrm{~S}>\mathrm{ZnS}>\mathrm{CuS}$
BETA
