Question

Indicate the steps in the preparation of :
(i) K2Cr2O7 from chromite ore.
(ii) KMnO 4 from pyrolusite ore.​

Answer 1

Answer:

Preparation of K2Cr2O7 It takes place in three steps: Conversion of chromite ore into sodium chromate 4FeCr2O4 + 4Na2CO3 + 7O2 → Na2CrO4 + Fe2O3 + 8CO2 Conversion of sodium chromate into sodium dichromate 2Na2CrO4 + 2H+ → Na2Cr2O7 + 2Na+ + H2O Conversion of sodium dichromate into potassium dichromate Na2Cr2O7 + 2KCl → K2 Cr2O7 + 2NaCl KMnO4 from pyrolusite ore The green mass can be extracted with water and then oxidized either electrolytically or /ozone into the solution. Electrolytic oxidation /indicate-the-steps-the-preparation-k2cr2o7-from-the-chromite-ore-and-kmno4-from-pyrolusite

Answer 2

i)Potassium dichromate is prepared from chromate ore by

4FeCrO4 + 16NaOH +7O2 –> 8NaCrO4 + 2Fe2O3 + 8H2O

Thus formed sodium chromate into sodium dichromate

2Na2CrO4 + conc H2SO4 –> Na2Cr207 + Na2SO4 + H2O

(ii) Potassium permanganate can be prepared from pyrolusite(MnO2)

2MnO2 + 4KOH +O2 –> 2K2MnO4 + 2H2O

thus obtained product can be extracted with water and then oxidized electrolytically