Question

Equal volumes of two solutions containing separately Ba²⁺ and SO₄^2- ions are mixed. Which will give a precipitate of BaSO₄? (K_SP for BaSO₄ = 1.5 x 10^–9).

(a) 10^-5 M Ba²⁺ and 10^-5 M SO₄^2-

(b) 10^-6 M Ba²⁺ and 10^-6 M SO₄^2-

(c) 10^-7 M Ba²⁺ and 10^-7 M SO₄^2-

(d) 10^-3 M Ba²⁺ and 10^-3 M SO₄^2-

Answer 1

Correct option: (c) 10^-7 M Ba²⁺ and 10^-7 M SO₄^2-

Explanation: 

When equal volumes of solutions are mixed, their concentration will be halved.

The ion product, Q, for (1)

We know that when Q > K_sp, precipitation occurs.

Given K_sp = 1.5 x 10^–9, and Q for (4) = 2.5 x 10^–7