Question

Effect of increasing ph on dichromate ion with help of structures reaction

Answer 1

Preparation of K2Cr2O7. It involves three steps: (i)Conversion of chromite ore into the sod. chromate. Ore is powdered and fused with in the presence of air when sodium chromate is formed.2FeO.Cr2O3 + O2
Fe2O3 + 2Cr2O3Chromite ore Cr2O3 + 2Na2 CO3 +  2Na2CrO4 + 2CO2 Sod. chromate(ii) Conversion of sodium chromate into sodium dichromate. Sodium chromate is acidified with 
to give sodium dichromate. 2Na2CrO4 + H2SO4Na2Cr2O7 Sodiumdichromate+Na2SO4 + H2O (iii)Conversion of sodium dichromate into potassium dichromate. Sodium dichromate is treated with KCI and the resulting solution is evaporated to get orange coloured crystals of potassium dichromate.Na2Cr2O7+2KCI K2Cr2O7 + 2NaCl Effect of pH. On increasing the pH of K2Cr2O7 solution, the dichromate ion canges to chromate ion.