describe the preparation of k2cr2o7 from chromite ore and explain the reaction of k2cr2o7 with acid FeSo4 , KI and H2S ?
K2Cr2O7 is prepared from the chromate ore. The steps involved are as follows:
(a) Preparation of sodium chromate
4FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2
(b) Conversion of sodium chromate into sodium dichromate.
2Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
(c) Conversion of sodium dichromate into potassium dichromate.
Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl
Chemical properties:
- - Reaction with Acidic FeSO4: Ferric sulphate is formed
K2Cr2O7 + 7H2SO4 + 6FeSO4 → K2SO4 + Cr2(SO4)3 + 3Fe2(SO4)3 + 7H2O
- - Reaction with KI: Iodine is released
K2Cr2O7 + 7H2SO4 + 6Kl → 4K2SO4 + Cr2(SO4)3 + 3l2 + 7H2O
- - Reaction with H2S: Sulphur is formed.
K2Cr2O7 + 4H2SO4 + 3H2S → K2SO4 + Cr2(SO4)3 + 7H2O + 3S