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

Explanation

Finely powdered chromite ore is mixed with soda ash and quicklime. The mixture is then roas in a reverberatory furnace in presence of excess of air a yellow mass containing sodium chromat obtained.
`4FeCr_(2)O_(4)+8Na_(2)CO_(3)+7O_(2) to 2Fe_(3)O_(3)+8Na_(2)CrO_(4)+8CO_(2)`
Coversion of sofium chromate to sodium dichromate: Sodium chromate is treated with concentrated sulphuric to form sodium dichromate.
`2Na_(2)CrO_(4)+H_(2)SO_(4)toNa_(2)Cr_(2)O_(7)+Na_(2)SO_(4)+H_(2)O`.
Conversion of sodium dichromate to potassium dichromate Sodium dichromate solution is heated to concentrate Now a calculated quantity of potassium chloride is added on Cooling, the least soluble potassium dichromate separate out as crystals
`Na_(2)Cr_(2)O_(7)+2KCl to K_(2)Cr_(2)O_(7)+2NaCl`