An aqueous solution contains `Ni^(2+), Co^(2+), Pb^(2+)` ions at equal concentrations. The solubility product of NiS, PbS and CoS in water at `25^@C` are respectively given below. Indicate which of these ions will be precipitated first and last when sulphide concentration is progressively increased from zero ?`[K_(sp) of NiS=3xx10^(-19), K_(sp) of CoS=4xx10^(-21), K_(sp) of PbS=3xx10^(-28)`

Options

A. NiS and PbS
B. NiS and CoS
C. CoS and NiS
D. PbS and NiS

Answer

D