Question

The solubility product of $CuS,{Ag}_{2}S$ and $HgS$ are ${10}^{-37},{10}^{-44}$ and ${10}^{-54}$ respectively. The solubility of these sulphides will be in the order:

• A. $HgS>{Ag}_{2}S>CuS$
• B. ${Ag}_{2}S>HgS>CuS$
• C. $CuS>{Ag}_{2}S>HgS$
• D. ${Ag}_{2}S>CuS>HgS$

Answer 1

The correct option is D ${Ag}_{2}S>CuS>HgS$

$CuS⟹S^2={10}^{-37}⟹S=3.16\times {10}^{-19}$

$A{g}_{2}S⟹4S^3={10}^{-44}⟹S=1.357\times {10}^{-15}$

$HgS⟹S^2={10}^{-54}⟹S=1.0\times {10}^{-27}$

Order of Solubility is:

$A{g}_{2}S>CuS>HgS$