Question

Discuss the method of preparation of potassium dichromate from chromite ore and write the structural formula of dichromate ion.

Hint:

Potassium dichromate is obtained by oxidation of chromite ore in an alkaline medium followed by acidification.

Answer 1

Step 1: Preparation Steps: \[ 4 FeCr_2O_4 + 8 Na_2CO_3 + 7 O_2 \rightarrow 8 Na_2CrO_4 + 2 Fe_2O_3 + 8 CO_2 \] \[ 2 Na_2CrO_4 + H_2SO_4 \rightarrow Na_2Cr_2O_7 + Na_2SO_4 + H_2O \] Step 2: Structural Formula of Dichromate Ion: \[ [\text{Cr}_2O_7]^{2-} \]