The cation that will not be precipitated by $\mathrm{H}_{2} \mathrm{~S}$ in the presence of dil. HCl is :
The cation that will not be precipitated by $\mathrm{H}_{2} \mathrm{~S}$ in the presence of dil. HCl is :
$\mathrm{Pb}^{2+}$
$\mathrm{Cu}^{2+}$
$\mathrm{Co}^{2+}$
$\mathrm{As}^{3+}$
Solution
$\mathrm{Co}^{+2}$ ion is precipitated by $\mathrm{H}_{2} \mathrm{~S}$ in presence of $\mathrm{NH}_{4} \mathrm{OH}$ which is a group reagent of group IV in cationic analysis.