1.

Describe the manufacture of potassium dichromate from chromite ore.

Answer»

Solution :(i) Preparation of `K_2Cr_2O` 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_2tounderset(("YELLOW solution"))(8Na_2CrO_4+2Fe_2O_3+8CO_2)`
(b) The solutio is filtered and TREATED with sulphuric acid
`2Na_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 tounderset("Potassium dichromate crystals")(K_2Cr_2O_7+2NaCl)`


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