Question

When $H_{2}S$ gas is passed through a hot acidic aqueous solution containing $A{l}^{3+},C{u}^{2+},P{b}^{2+}andN{i}^{2+},a$ precipitate is formed, which consists of

• A. $CuS$ and $A{l}_2{S}_3$
• B. $PbS$ and $NiS$
• C. $CuS$ and $NiS$
• D. $PbS$ and $CuS$

Answer 1

Answer: (D)

When $H_{2}S$ gas is passed through a hot acidic aqueous solution containing AI${}^{3+},C{u}^{2-},P{b}^{2+}$ and $N{i}^{2+},$ precipitate of only group $II$ cations is formed. Among the given cations, $P{b}^{2+}$ and $C{u}^{2+}$ lie in group $2$ cations.
$C{u}^{2+}+H_{2}S⟶\underset{(\text{ Black ppt. })}{\mathrm{CuS}}+2H^{+}$
$P{b}^{2+}+H_{2}S⟶\underset{(\text{ Black ppt. })}{\mathrm{PbS}}+2H^{+}$