The reaction with sodium
carbonate occurs as follows:
4 FeCr2O4 + 8 Na2CO3 + 7 O2 ® 8 Na2CrO4 + 2 Fe2O3 + 8 CO2
The yellow solution of sodium chromate is filtered and acidified
with sulphuric acid to give a solution from which orange sodium
dichromate, Na2Cr2O7 2H2O can be crystallised 2Na2CrO4 + 2 H
+ ® Na2Cr2O7 + 2 Na
+ + H2O
Rationalised 2023-24
106
Chemistry
Sodium dichromate is more soluble than potassium dichromate The latter is therefore, prepared by treating the solution of sodium
dichromate with potassium chloride