1.

Write the equations involved in the preparation of potassium dichromate from chromite ore.

Answer»

Solution :(i) Preparation of `K_2Cr_2O_7` 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.
`underset("Chromiteore")(4FeCr_2O_4+8Na_2CO_3+7O_2)tounderset("(Yellow solution)of Sodium chromite")(8Na_2CrO_4+2Fe_2O_3+8CO_2)`
The solution is filtered and TREATED with SULPHURIC acid
`Na_2CrO_4+H_2SO_4tounderset("Sodium dichromate")(Na_2Cr_2O_7+Na_2SO_4+H_2O)`
(C) Now sodium dichromate is treated with potassium chloride. As a result potassium dichromate is poduced
`Na_2Cr_2O_7+2KCltounderset(potassium dichromate crystal")(K_2Cr_2O_7+2NaCl)`


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