Question

At 25 °C only 0.0650 mol of the generic salt AB2 is soluble in 1.00 L of water. What is the Ksp of the salt at 25 °C?

Answer 1

Concentration of AB₂ is S = Number of moles / Volume of solution in L

                                  = 0.0650 mol / 1.00 L

                                    = 0.0650 M

AB₂ A⁺ + 2B^-

1 mole of AB₂ produces 1 mole of A+ & 2 moles of B-

So [A⁺] = [AB₂ ] = 0.0650 M

     [B^-] = 2[AB₂] = 2x0.0650 M = 0.130 M

Solubility product constant , K_sp = [A⁺] [B^-]²

                                                = 0.0650 x 0.130²

                                                = 1.098x10^-3

Therefore K_sp of the salt at 25 °C is 1.098x10^-3