Question

A sample of a chromium-containing alloy weighing 3.450 g was dissolved in acid, and all the chromium in the sample was oxidized to 2CrO42–. It was then found that 3.18 g of Na2SO3 was required to reduce the 2CrO42– to CrO2– in a basic solution, with the SO32– being oxidized to SO42–.
Write a balanced equation for the reaction of 2CrO42– with SO32- in a basic solution.

Answer 1

Answer:

H_2O + 2CrO_4^2- + 3SO_3^2- -> 3SO_3^2- + 2CrO_2^- + 2OH^-

Explanation:

Reduction half reaction

2H_2O + CrO_4^2- + 3e -> CrO_2^- + 4OH^-

Oxidation half reaction

2OH^- + SO_3^2- -> SO_4^2- + H_2O + 2e

Balanced overall equation

H_2O + 2CrO_4^2- + 3SO_3^2- -> 3SO_3^2- + 2CrO_2^- + 2OH^-