A solution containing a mixture of 0.0381 M potassium chromate (K2CrO4) and 0.0769 M sodium oxalate (Na2C2O4) was titrated with a solution of barium chloride (BaCl2) for the purpose of separating CrO42– and C2O42– by precipitation with the Ba2 cation. Answer the following questions regarding this system. The solubility product constants (Ksp) for BaCrO4 and BaC2O4 are 2.10 × 10-10 and 1.30 × 10-6, respectively.

Question

A) Which will precipitate first? BaCrO4 or BaC2O4

B) What concentration of Ba2 must be present for BaCrO4 to begin precipitating?

C) What concentration of Ba2 is required to reduce oxalate to 10% of its original concentration?

D) What is the ratio of oxalate to chromate ([C2O42–]/[CrO42–]) when the Ba2 concentration is 0.0050 M?

Answer 1

A) BaCrO4