Question

An aqueous solution of a substance gives a white precipitate on treatment with dilute hydrochloric acid, which dissolves on heating. When hydrogen sulphide is passed through the hot acidic solution, a black precipitate is obtained. The substance is a :

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

Answer 1

The correct option is D $P{b}^{2+}salt$

Option (D) is correct.

The substance is a $P{b}^{2+}$ salt.

A white precipitate which is soluble in hot water is lead chloride.

$\begin{array}{cccccc}P{b}^{2+}& +& 2HCl& ⟶& PbC{l}_2\downarrow +& 2H^{+}\\ & & & & White& \end{array}$

$\begin{array}{ccccccc}PbC{l}_2& +& H_{2}S& \stackrel{H^{+}}{\to }& PbS\downarrow & +& 2HCl\\ Hotsolution& & & & Black& & \end{array}$