The correct option is C 4×10−12 mol2L−2
Given, solubility, s=2×10−6 mol L−1
Lets consider solid CdCO3 is in contact with its saturated aqueous solution. The equilibrium is established between undissolved CdCO3 and its ions. The equilibrium reaction is given by :
CdCO3(s)⇌Cd2+(aq)+CO2−3(aq) t=0 c 0 0t=teq c−s s s
Solubility product: Ksp=[Cd2+][CO2−3]=s×s
s2=(2×10−6)2Ksp=4×10−12 mol2L−2