The Ksp of Ag2CrO4,AgCl,AgBr and AgI are respectively, 1.1×10−12,1.8×10−10,5.0×10−13,8.3×10−17. Which one of the following salts will precipitate last if AgNO3 solution is added to the solution containing equal moles of NaCl, NaBr, Nal and Na2CrO4?
Ag2CrO4
Let the concentration of NaCl, NaBr, NaI and Na2CrO4 be 1M.
Ksp(Ag2CrO4)=[Ag+]2[CrO2−4]=4s3 where s is the solubility and the concentartion of the chromate ion.
[Ag+]Ag2CrO4=√Ksp(Ag2CrO4)[CrO2−4]=√1.1×10−12(1.1×10−12/4)1/3
[Ag+]AgI=Ksp(AgI)[I−]=8.3×10−171
[Ag+]AgCl=Ksp(AgCl)[Cl−]=1.8×10−101
[Ag+]AgBr=Ksp(AgBr)[Br−]=5.0×10−13
∴ Solubility of Ag2CrO4 is the highest it will precipitate last