Question:
To an aqueous solution containing ions such as $\mathrm{Al}^{3+}, \mathrm{Zn}^{2+}, \mathrm{Ca}^{2+}, \mathrm{Fe}^{3+}, \mathrm{Ni}^{2+}, \mathrm{Ba}^{2+}$ and $\mathrm{Cu}^{2+}$ was added conc. $\mathrm{HCl}$, followed by $\mathrm{H}_{2} \mathrm{~S}$.
The total number of cations precipitated during this reaction is/are :
Correct Option: 1
Solution:
$\mathrm{Al}^{3+}$ and $\mathrm{Fe}^{3+}$ sulphides hydrolyse in water.
$\mathrm{Ni}^{2+}$ and $\mathrm{Zn}^{2+}$ require basic medium with $\mathrm{H}_{2} \mathrm{~S}$
to form ppt
$\mathrm{Ca}^{2+}$ and $\mathrm{Ba}^{2+}$ sulphides are soluble
hence we will receive only CuS ppt.