Question

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

Answer 1

Preparation of Potassium dichromate (K₂Cr₂O₇):
Step I : Iron chromite to sodium chromate:
FeCr₂O₄ + Na₂CO₃ + O₂ → Na₂CrO₄ + Fe₂O₃ + CO₂

Step II : Sodium dichromate to potassium dichromate:

Step III : Sodium chromate to potassium dichromate :

Effect of pH:
With increase in pH, potassium dichromate converts in potassium chromate: