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

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Question : 9
Total: 31
State the role of silica in the metallurgy of copper.
Solution:  
Iron present in pyrites has greater affinity for oxygen than copper. The copper oxide formed reacts with unchanged iron sulphide to form iron oxide so, most of the iron sulphide is oxidised to ferrous oxide.
2FeS+3O2 2FeO+2SO2
Ferrous oxide combines with silica which acts as flux and forms ferroussilicate. By this reaction most of the iron is removed as slag.
FeO+
SiO2
Flux
FeSiO3
Ferroussilicate
(slag)
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