Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?
Potassium dichromate is prepared from chromite ore (FeCr2O4) in the following steps.
Step (1):
Preparation of sodium chromate
4FeCr2O4 + 16NaOH + 7O2 → 8NaCrO4 + 2Fe2O3 + 8H2O
Step (2):
Conversion of sodium chromate into sodium dichromate
2Na2CrO4 + conc.H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
Step(3): Conversion of sodium dichromate to potassium dichromate
Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl
Potassium dichromate being less soluble than sodium chloride is obtained in the form of orange coloured crystals and can be removed by filtration.
The dichromate (Cr2O2-7) ion exists in equilibrium with chromate (CrO2-4) ion at pH 4. However, by changing the pH, they can be interconverted.
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Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 14: Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of incre....
Comments
What is the use of studying this
there is a mistake in Na balancy
very good
Thanks
The product of 1st reaction is 8Na2CrO4 instead of 8NaCrO3
Very nice illustration
How chromite ore react with potassium carbonate
This is very helpful for me