Question

Write reactions involved in preparation of potassium dichromate from chrome iron ore.

Answer 1

Reactions involved in the preparation of potassium dichromate from chrome iron ore (chromite ore):

a. Conversion of chrome iron ore into sodium chromate (Roasting): 

4FeO.Cr₂O₃ (Chrome iron ore) + 8Na₂CO₃ (Sodium carbonate) + 7O₂ (Oxygen) → 2Fe₂O₃ (Ferric oxide) + 8Na₂CrO₄ (Sodium chromate) + 8CO₂ (Carbon dioxide)

b. Conversion of sodium chromate into sodium dichromate:

2Na₂CrO₄ (Sodium chromate) + H₂SO₄ (conc.) → Na₂Cr₂O₇ (Sodium dichromate)+ Na₂SO₄ (Sodium sulphate) + H₂O

c. Conversion of sodium dichromate into potassium dichromate:

Na₂Cr₂O₇ (Sodium dichromate) + 2KCl (Potassium chloride) → K₂Cr₂O₇ (Potassium dichromate) + 2NaCl (Sodium chloride)