Question:
Indicate the steps in the preparation of:

(i) K₂Cr₂O₇ from chromite ore.

(ii) KMnO₄ from pyrolusite ore.

Answer:

(i) Potassium dichromate (K₂Cr₂O₇) is prepared from chromite ore (FeCr₂O₄) in the following steps.

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 (Cr₂O²_-7) ion exists in equilibrium with chromate (CrO^2-₄) ion at pH 4. However, by changing the pH, they can be interconverted.

(ii) Potassium permanganate (KMnO₄) can be prepared from pyrolusite (MnO2). The ore is fused with KOH in the presence of either atmospheric oxygen or an oxidising agent, such as KNO₃or KClO₄, to give K₂MnO₄.

The green mass can be extracted with water and then oxidized either electrolytically or by passing chlorine/ozone into the solution.

Electrolytic oxidation

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Question:
Indicate the steps in the preparation of:

(i) K₂Cr₂O₇ from chromite ore.

(ii) KMnO₄ from pyrolusite ore.

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Question: Indicate the steps in the preparation of: (i) K2Cr2O7 from chromite ore. (ii) KMnO4 from pyrolusite ore.

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Question:
Indicate the steps in the preparation of:

(i) K₂Cr₂O₇ from chromite ore.

(ii) KMnO₄ from pyrolusite ore.