Write the balanced chemical equation involved in the manufacture of potassium- dichromate from chromite ore.

Explanation

`K_(2)Cr_(2)O_(7)` is manufactured from chromite ore (or) chrome iron stone `FeO.Cr_(2)O_(3)` (or) `FeCr_(2)O_(4)`.
Step 1 :- Chromite ore is heated with sodium carbonate in excess of air to form sodium chromate.
`4FeCr_(2)O_(4)+8Na_(2)CO_(3)+7O_(2)rarr 8Na_(2)CrO_(4)+2Fe_(2)O_(3)+8CO_(2)`
Step 2 :- The yellow solution of sodium chromate is filtered and acidified with sulphuric acid to give orange solution of sodium dichromate.
`2Na_(2)CrO_(4)+H_(2)SO_(4)rarr Na_(2)Cr_(2)O_(7)+Na_(2)SO_(4)+H_(2)O`
Step 3 :- The solution of sodium dichromate is treated with KCl to form potassium dichromate
`Na_(2)Cr_(2)O_(7)+2KCl rarr K_(2)Cr_(2)O_(7)+2NaCl`
Solution on cooling gives orange red crystals of `K_(2)Cr_(2)O_(7)`