Question

A solution containing a mixture of 0.0379 M potassium chromate ( K2CrO4 ) and 0.0739 M sodium oxalate ( Na2C2O4 ) was titrated with a solution of barium chloride ( BaCl2 ) for the purpose of separating CrO2−4 and C2O2−4 by precipitation with the Ba2+ cation. The solubility product constants ( Ksp ) for BaCrO4 and BaC2O4 are 2.10×10−10 and 1.30×10−6 , respectively. Which barium salt will precipitate first?

Answer 1

Answer:

BaCrO₄ will precipitate first.

Explanation:

For a generic salt (AB) that is soluble in some solvent, the solubility product constant (Kps) is:

AB(s) ⇄ A⁺ + B⁻

Kps = [A⁺]*[B⁻]

So, as greater is Kps, as higher is the solubility, and more difficult will be to form a precipitated (the solid form of the salt).

Kps of BaCrO₄ < Kps of BaC₂O₄, so BaCrO₄ will precipitate first.