When calcium hydroxide dissolves, it dissociates into Ca(OH)2 = Ca2+ and 2OH- Let's assign the variable X for the solubility of Ca2+ and OH I.e Ca2+ = X and 2OH- = 2X Then Ksp = [Ca2+][OH-]^2 So we have (X) (2X)^2 = 5.02 * 10^(-6) 4X^3 = 5.02 * 10 ^(-6) X^3 = 5.02 * 10^(-6) / 4 X^3 = 0.003110 X = 0.1459