Example IonicEq 7.32 Solubility product Value of solubility product of lead iodate Pb(IO3)2 at 25C is equal to 2.61013. Precipitate of lead iodate was washed at temperature 25C by a) pure water; b) solution of Pb(NO3)2[c(Pb(NO3)2)=0.05moldm3,]; c) solution of KIO3[c(KIO3)=0.05moldm3]. Calculate solubility of Pb(IO3)2 for each case. Which washing liquid (water or two above solutions) should be selected for washing to minimize the loss of the precipitate? (standard state of electrolytes: standard solution at concentration cst=1moldm3 ). Assume ideal behavior of the solution (i.e. i=1 ). Pb(IO3)2(s)1Pb2++2IO3Ks=(aPb(O3)2)11(aPb2)1(aIO3)2=(cst)3(cPb2+)1(cIO3)2 Solution: a) pure water b) solution of Pb(NO3)2(cPb(NO3)2=0.05mol/dm3) Ks=(cst)3(c+0.05)1(2c)2(cst)3(0.05)1(2c)2 c) solution of KIO3(cKIO3=0.05mol/dm3) Ks=(cst)3(c)1(2c+0.05)2(cst)3(c)1(0.05)2 Results: b) c=20.014Ks=mol/dm3 c) c=(0.05)2Ks=mol/dm3