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

Explanation

The dichromate and chromate ions exist in equilibrium at pH = 4
`Cr_2O_7^(2-) + H_2O overset(pH = 4)(iff) 2CrO_4^(2-) + 2H^+`
On increasing pH (by adding alkali), the ` H^+` ions are used up and according to Le-Chatelier.s principle, the reaction proceeds towards the forward direction producing yellow chromate ions. On decreasing pH (by adding an acid), the reaction shifts towards the backward direction producing the orange dichromate ion.