• # question_answer Through a solution containing $C{{u}^{2+}}$ and $N{{i}^{2+}},\,{{H}_{2}}S$ gas is passed after adding dil $HCl,$ which will precipitate out and why?

$C{{u}^{2+}}$ will precipitate out because in the acidic medium, only ionic product $[C{{u}^{2+}}]\,[{{S}^{2-}}]$ exceeds the solubility product of CuS.