Question

An aqueous solution of a mixture of two inorganic salts, when treated with dilute $HCl$, gave a precipitate $(P)$ and filtrate $(Q)$. The precipitate $(P)$ was found to dissolve in hot water. The filtrate $(Q)$ remained unchanged, when treated with $H_{2}S$ in a dilute mineral acid medium. However, it gave a precipitate $(R)$ with $H_{2}S$ in an ammoniacal medium. The precipitate $R$ gave a coloured solution $(S)$, when treated with $H_2{O}_2$ in an aqueous $NaOH$ medium.
The precipitate $P$ contains
(1) $P{b}^{2+}$
(2) $H{g}_2^{2+}$
(3) $A{g}^{+}$
(4) $H{g}^{2+}$

• A. $P{b}^{2+}$
• B. $H{g}_2^{2+}$
• C. $A{g}^{+}$
• D. $H{g}^{2+}$

Answer 1

Answer: (A)

PLAN $PbC{l}_2$ is soluble in hot water.
In ammoniacal medium, cations of group III and IV may be precipitated as hydroxide or sulphide and dissolved in $H_2{O}_2$ due to oxidation.
Thus, $P$ is $P{b}^{2+}.$