The maximum allowable concentration of pb2 + ions in drinking water is 0.05 ppm (i. e., 0.05 g of pb2 + in 1 million grams of water). (a) what is the pb2 + concentration of an underground water supply at equilibrium with the mineral anglesite (pbso4) (ksp = 1.6 * 10-8) ?

PbSO₄ partially dissociates in water. the balanced equation is;

PbSO₄ (s) ⇄ Pb²⁺ (aq) + SO₄²⁻ (aq)

Initial - -

Change - X + X + X

Equilibrium X X

Ksp = [Pb²⁺ (aq) ] [SO₄²⁻ (aq) ]

1.6 x 10⁻⁸ = X * X

1.6 x 10⁻⁸ = X²

X = 1.3 x 10⁻⁴ M

Hence the Pb²⁺ concentration in underground water is 1.3 x 10⁻⁴ M.

[Pb²⁺] = 1.3 x 10⁻⁴ M.

= 1.3 x 10⁻⁴ mol / L x 207 g / mol

= 26.91 ppm