Question

Which one among the following pairs of ions cannot be separated by $H_{2}S$ in the presence of dilute hydrochloric acid?

• A. $B{i}^{3+}$, $C{d}^{2+}$
• B. $A{l}^{3+}$, $H{g}^{2+}$
• C. $Z{n}^{2+}$, $C{u}^{2+}$
• D. $N{i}^{2+}$, $C{u}^{2+}$

Answer 1

The correct option is A $B{i}^{3+}$, $C{d}^{2+}$

Option (A) is correct.
Both $B{i}^{3+}$ and $C{d}^{2+}$ will be precipitated as $B{i}_2{S}_3$ (black) and $CdS$ (yellow) by $H_{2}S$ as both have low values of $K_{sp}$ than $A{l}^{3+}$, $Z{n}^{2+}$ and $N{i}^{2+}$ (as sulphides).