question_answer

An aqueous solution contains\[N{{i}^{2+}},C{{o}^{-28}}\]and\[P{{b}^{2+}}\]ions    at    equal concentrations. The solubility product of\[NiS,\text{ }PbS\]and\[CoS\]in water at\[25{}^\circ C\]are\[1.4\times {{10}^{-24}},\text{ }3.4\times {{10}^{-28}}\]and \[3\times {{10}^{-26}},\]respectively. Indicate which of these ions will be precipitated first and last   when   sulphide   concentration   is progressively increased from zero?

A) \[NiS\]and \[PbS\]         

B)  \[NiS\]and \[CoS\]

C) \[CoS\]and\[NiS\]          

D) \[PbS\]and\[NiS\]