Question

`H_2 S` in the presence of HCl precipitate group II but not group IV because
A. HCl activates `H_(2)S`
B. HCl incraeses the concentration of `Cl^(-)`
C. HCl decreases the concentration of `S^(2-)` ions
D. HCl lowers the solubility of `H_(2)S` in the solution

Answer 1

Due to common ion effect, HCl suppresses the ionisation of `H_(2)S` thus decreasing the concentration of `S^(2-)` ions. Only group II radicals are precipitated.