The molar solubility is the Pb ions present. PbCO3 dissociate to form Pb ions and CO3 ions Ksp 7.40x10^-14 is equal to (Pb ions) (CO3 ions) Pb ions correspond to CO3 ions (pb ions)( Pb ions) is equal to 7.40x10^-14 therefore Pb ions is square root of 7.4x10^14 which is 2.27x10^-7m In g/l is (2.27x10^-7) x 267(RFM of PbCO3) which is 6.06x10^-5 g/l