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NCERT Class XII Chemistry
Chapter - General Principle of Process of Isolation of Elements
Questions with Solutions

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Question : 13 of 31
Marks: +1, -0
How can you separate alumina from silica in a bauxite ore associated with silica? Give equations, if any.
Solution:  
Serpeck’s process is used when silica is present in considerableamounts in bauxite ore. The ore is mixed with coke and heated at 1800°Cin presence of nitrogen, where AlN is formed.
Al2O3+3C+N2→2AlN+3CO\mathrm{Al}_2\mathrm{O}_3 + 3\mathrm{C} + \mathrm{N}_2 \rightarrow 2\mathrm{AlN} + 3\mathrm{CO}
Silica is reduced to silicon which volatilises off at this temperature.
siO2+2C→Si+2CO\mathrm{siO}_2 + 2\mathrm{C} \rightarrow \mathrm{Si} + 2\mathrm{CO}
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