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What is the use of lime stone in the preparation of potassium dichromate from chromite ore ? What is the use of lime stone in the preparation of potassium dichromate from chromite ore ?
Manufacturing of potassium dichromate from chrornate ore :-Chromate ore i.e. FeO, Cr2O3is also called chrome iron ore and it is converted in potassium dichromate as follows. .i) Concentration of ore : By washing the powdered chromate ore with water lighter impurites are removed leaving behind the heaviour ore.ii) Roasting : Conversion of chromite ore in sodium chromate :Concentrated ore is heated with sodium carbonate and lime stone in reverberatory furnance in air to form yellow sodium chromate.Lime stone is added to keep the reaction mixture porous.4FeO Cr2O3+ 8Na2CO3+ 7O2-----> 2Fe2O3+ 8Na2CrO4+ 8CO2.Sodium chromate is seperated by dissolving in water.iii) Conversion of sodium chromate into sodium dichromate : Sodium chromate on reacting with H2SO4(cone.) produce sodium dichromate.2Na2CrO4+ H2SO4-----» Na2Cr2O7+ Na2SO4+ H2OSodium sulphate is separated by concentration of solution on filteration aqueous solution of Na2Cr2O7is obtained.iv) Conversion of sodium dichromate into potassium dichromate : Sodium dichromate on reacting with KC1 form K2Cr2O7. Na2Cr2O7+ 2KC1 -----> K2Cr2O7+ 2NaCl.Less soluble K2Cr2O7is seperated on cooling and it is purified by crystalization.Thanks & RegardsRinkoo GuptaAskIITians Faculty
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