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Solution - Indicate the steps in the preparation of K2Cr2O7 from chromite ore. - CBSE (Science) Class 12 - Chemistry

Question

Indicate the steps in the preparation of K2Cr2O7 from chromite ore.

Solution

Potassium dichromate (`K_2Cr_2O_7`) is prepared from chromite ore (`FeCr_2O_4`)in the following steps.

Step (1): Preparation of sodium chromate

`4FeCr_2O_4 + 16NaOH + 7O_2 ->8Na_2CrO_4 + 2Fe_2O_3 + 8H_2O`

Step (2): Conversion of sodium chromate into sodium dichromate

`2Na_2CrO_4 + conc.H_2SO_4 -> Na_2Cr_2O_7+Na_2SO_4+H_2O`

Step(3): Conversion of sodium dichromate to potassium dichromate

`Na_2Cr_2O_7 + 2KCl -> K_2Cr_2O_7 + 2NaCl`

Potassium chloride being less soluble than sodium chloride is obtained in the form of orange coloured crystals and can be removed by filtration.

The dichromate ion (`Cr_2O_7^(2-)`) exists in equilibrium with chromate (`CrO_4^(2-)`) ion at pH 4. However, by changing the pH, they can be interconverted.

Is there an error in this question or solution?

APPEARS IN

 NCERT Chemistry Textbook for Class 12 Part 1 (with solutions)
Chapter 8: The d-block and f-block Elements
Q: 26.1 | Page no. 235

Reference Material

Solution for question: Indicate the steps in the preparation of K2Cr2O7 from chromite ore. concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals. For the courses CBSE (Science), CBSE (Arts), PUC Karnataka Science, CBSE (Commerce)
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