How is potassium dichromate prepared from a sample of chromite ore ? Give balanced equations for the chemical reactions involved.

Explanation

Preparation of potassium dichromate from chromite ore involves following steps:
(1) Conversion of chromite ore to sodium chro mate by roasting finely powdered chromite ore with sodium carbonate and quick lime in excess of air.
`{:(4FeCr_2O_4 + 8Na_2CO_3 +7O_2 overset(CaO+air)to),("Chromite " " Sodium"),("ore " " carbonate"):}`
`{:(2FeCr_2O_3 + 8Na_2CO_4 +8CO_2 ),("Ferric " " Sodium"),("oxide " " chromat"):}`
(2) Conversion of sodium chromate to sodium dichromate by the action of conc. `H_2SO_4`
`{:(2Na_2CrO_4 + H_2SO_4 to),(conc.), (Na_2Cr_2O_7 + Na_2SO_4 + H_2O),("Sodium"),("dichromate"):}`
(3) Conversion of sodium dichromate to potas sium dichromate by treating it with KCl solution.
`{:(Na_2Cr_2O_7 + 2KCl to K_2Cr_2O_7 + 2NaCl),("Potassium"),("dichromate"):}`
From resulting solution potassium dichromate is crystallised.