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

<p><strong>8.24&nbsp;</strong>Potassium dichromate is prepared from chromite ore (FeCr₂O₄) by the following steps:</p><p>Step1: Preparation of sodium dichromate in the reaction of Chromite ore with sodium hydroxide and oxygen gas.</p><p>4FeCr₂O₄ + 16NaOH + 7O₂? 8Na₂CrO₄ + 2Fe₂O₃ + 8H₂O</p><p>Step2: Conversion of Sodium Chromate on reaction with concentrated Sulfuric acid gives Sodium dichromate as a product.</p><p>2Na₂CrO₄ + conc. H₂SO₄? Na₂Cr₂O₇ + Na₂SO₄ + H₂O</p><p>Step3: Sodium dichromate on reaction with potassium chloride converts to potassium dichromate as a product.</p><p>Na₂Cr₂O₇ + 2KCl? K₂Cr₂O₇ + 2NaCl</p><p>As potassium dichromate is less soluble than sodium chloride so, potassium dichromate is obtained in form of orange crystals.</p><p>Dichromate ion exists in equilibrium with chromate ion at around pH. However, by changing the pH they can be interconverted.</p>

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