MetallurgyHard
Question
In the extraction of aluminium
Process X : employed for red bauxite to remove iron oxide (main impurity)
Process Y : (Serpeck′s process) : used for white bauxite to remove Z (main impurity) then,
Select correct option for the process X and impurity Z.
Process X : employed for red bauxite to remove iron oxide (main impurity)
Process Y : (Serpeck′s process) : used for white bauxite to remove Z (main impurity) then,
Select correct option for the process X and impurity Z.
Options
A.X = Hall and Heroult′s process and Z = SiO2
B.X = Bayer′s process and Z = SiO2
C.X = Serpeck′s process and Y = iron oxide
D.X = Bayer′s process and Y = iron oxide
Solution
(X) Red bauxite contains the impurities of oxides of iron and silicates. In Bayer process, alumina isdissolved by reacting sodium hydroxide solution leaving behind the insoluble oxide of iron.
(Y) White bauxite contains the impurity of silica which is removed by Serpeck′s method.
Al2O3 + N2 + 3C
2AlN + 3CO ; SiO2 + 2C 
Si ↑+ 2CO↑
AlN + 3H2O → Al(OH)3↓ + NH3 ; 2Al(OH)3
Al2O3 + 3H2O
(Y) White bauxite contains the impurity of silica which is removed by Serpeck′s method.
Al2O3 + N2 + 3C
2AlN + 3CO ; SiO2 + 2C Si ↑+ 2CO↑AlN + 3H2O → Al(OH)3↓ + NH3 ; 2Al(OH)3
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