JEE Main · 2008 · 27 Apr 2008 · Offline · General Principles and Processes of Isolation of Metals

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Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?

(A)Metal sulphides are thermodynamically more stable than $CS_{2}$ ✓ Correct
(B) $CO_{2}$ is thermodynamically more stable than $CS_{2}$
(C)Metal sulphides are less stable than the corresponding oxides
(D) $CO_{2}$ is more volatile than $CS_{2}$

Answer: (A)

Solution

Sulphide ores are roasted to the oxide first because the oxide is far easier to reduce with carbon than the sulphide is, and this is underpinned by the greater stability and ready escape of

C O_{2}

compared with the

C S_{2}

that a direct reduction would have to form. The remark that metal sulphides are more stable than

C S_{2}

, while true in itself, is not what decides the choice of route, so among the factors listed it is the one of no real significance to roasting the sulphide before reduction.

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

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JEE Main · 2008 · 27 Apr 2008 · Offline · General Principles and Processes of Isolation of Metals

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