Question

The pair(s) of ions where both the ions are precipitated upon passing $H_{2}S$ gas in presence of dilute $HCl$, is/are:

• A. $B{a}^{2+},Z{n}^{2+}$
• B. $B{i}^{3+},F{e}^{3+}$
• C. $C{u}^{2+},P{b}^{2+}$
• D. $H{g}^{2+},B{i}^{3+}$

Answer 1

Answer: (C), (D)

$H{g}^{2+},B{i}^{3+}$

Group $2$ cations will be precipitated as sulphides when treated with $H_{2}S$ gas in presence of dilute $HCl$.
$C{u}^{2+}+H_{2}S\stackrel{H^{+}}{\to }CuS\downarrow$
$P{b}^{2+}+H_{2}S\stackrel{H^{+}}{\to }PbS\downarrow$
$H{g}^{2+}+H_{2}S\stackrel{H^{+}}{\to }HgS\downarrow$
$2B{i}^{2+}+3H_{2}S\stackrel{H^{+}}{\to }B{i}_2{S}_3\downarrow$