Explain the manufacture of Potassium dichromate from chromite ore.

Explanation

(1) Chromine ore is heated with sodium carbonate in excess of air to form sodium chromate .
`4 FeCr_(2)O_(4) +8Na_(2)CO_(3) +7O_(2) to 8Na_(2) CrO_(4) +2Fe_(2)O_(3) +8CO_(2)` (2) Sodium chromate is filtered and acidified with sulphuric acid to give sodium dichromate
`2Na_(2) CrO_(4) +H_(2)SO_(4) to Na_(2)Cr_(2)O_(7)+ Na_(2)SO_(4) +H_(2)O` (3) Sodium dichromate is treated with KCl to form potassium dichromate.
`Na_(2) Cr(2)O_(7)+2KCI to K_(2)Cr_(2)O_(7) +2NaCl`