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← IIT-JEE 2010 · Paper 1
ChemistrySingle correct+3 / -1Question 14 of 84

IIT-JEE 2010 · Paper 1, Chemistry question 14

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Paragraph for Questions 14 to 16

Copper is the most noble of the first row transition metals and occurs in small deposits in several countries. Ores of copper include chalcanthite (CuSOX4 ⋅ 5 HX2O\ce{CuSO4.5H2O}), atacamite (CuX2Cl(OH)X3\ce{Cu2Cl(OH)3}), cuprite (CuX2O\ce{Cu2O}), copper glance (CuX2S\ce{Cu2S}) and malachite (CuX2(OH)X2COX3\ce{Cu2(OH)2CO3}). However, 80% of the world copper production comes from the ore chalcopyrite (CuFeSX2\ce{CuFeS2}). The extraction of copper from chalcopyrite involves partial roasting, removal of iron and self-reduction.

Partial roasting of chalcopyrite produces

Choose one option
Answer and worked solution

Official answer: A

Partial roasting (in limited air) oxidises the iron sulphide preferentially, because iron has a higher affinity for oxygen than copper:
2 CuFeSX2+OX2→CuX2S+2 FeS+SOX2,2 FeS+3 OX2→2 FeO+2 SOX2.\ce{2CuFeS2 + O2 -> Cu2S + 2FeS + SO2},\qquad\ce{2FeS + 3O2 -> 2FeO + 2SO2}.
Copper stays as CuX2S\ce{Cu2S} and iron becomes FeO.

(A)