(1) Mg(OH)2(s) <==> Mg2+(aq) + 2OH-(aq)
-----x-------------------x-------------2x mol/L
Ksp =[Mg2+]*[OH-] ^2 = x*(2x)^2 =4x^3
x^3 = Ksp/4
(2) Ag2CrO4(s) <==> 2Ag+(aq) + CrO4^2
-----x-------------------2x----------------x mol/L
Ksp =[Ag+]^2*[CrO4^2 ]= x*(2x)^2 =4x^3
x^3 = Ksp/4
开3次方不方便!