Question

Consider the reaction

CaSO₄(s) Ca²⁺(aq) + SO₄^2-(aq)

At 25 °C, the equilibrium constant is K_c = 2.4 × 10^–5 for this reaction. (a) If excess CaSO₄(s) is mixed with water at 25 °C to produce a saturated solution of CaSO₄, what are the equilibrium concentrations of Ca²⁺ and SO₄^2-? (b) If the resulting solution has a volume of 1.4 L, what is the minimum mass of CaSO₄(s) needed to achieve equilibrium?

The equilibrium concentrations of Ca²⁺ and SO₄^2- are 4.9×10^–3 M.

b) The minimum mass of CaSO₄(s) needed to achieve equilibrium corresponds to the molarity equal to the equilibrium solubility of Ca²⁺ and SO₄^2– ions. We need to add at least