Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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221.
The method of zone refining of metals is based on the principle of
A
greater noble character of the solid metal than that of the impurity
B
greater solubility of the impurity in the molten state than in the solid
C
greater mobility of the pure metal than that of impurity
D
higher melting point of the impurity than that of the pure metal
Answer :
greater solubility of the impurity in the molten state than in the solid
The method of zone refining of metals is based on the principle of greater solubility of the impurity in the molten state than in the solid. Elements which are used as semiconductors like $$Si, Ge, Ga$$ etc, are refined by this method. Gallium arsenide and indium antimonide ( also used as semiconductor ) are also refined by this method.
222.
Sulphide ores are converted to oxides before reduction. This is explained on the basis of which of the following?
A
Sulphides cannot be reduced easily while oxides can be reduced easily.
B
Sulphides decompose on reduction hence they are first converted to oxides.
C
Sulphide ores have higher melting points than oxides.
D
Oxides are more stable than sulphides hence easy to reduce.
Answer :
Sulphides cannot be reduced easily while oxides can be reduced easily.
Thermodynamically based on Ellingham diagram it is observed that sulphides cannot be reduced easily as compared to oxides.