Write the balanced equations in the manufacture of potassium dichromate from chromite ore.

Explanation

(i) Preparation of `K_2Cr_2O_2`from chromite ore (a) Potassium dichromate is obtained by the fusion of chromite ore `(FeCr_2O_4)` with sodium (or potassium) carbonate in the presence of excess of air. `4FeCr_2O_4+8Na_2CO_3+7O_2 to 8Na_2CrO_4 + 2Fe_2O_3+8CO_2` (b) The solution is filtered and treated with sulphric acid. `Na_2CrO_4+H_2SO_4toNa_2Cr_2O_7+Na_2SO_4+H_2O` (c) Now sodium dichromate is treated with potassium chloride. As a result, potassium dichromate is produced. `Na_2Cr_2O_7+2KCl to K_2Cr_2O_7+2Nacl` (iii) Effect of increasing pH on `K_2Cr_2O_7` solution. `Cr_2O_7^2-+2OH^-to CrO_4^2-+H_2O. `