Explain the purification of sulphide ore by froth floatation method.

Froth floatation is used for separating gangue from sulphide ores. In this method, a suspension of the powdered ore is prepared with water. To it, froth stabilizers and collectors are added. The Froth floatation method can be used to separate two sulphide ores by adjusting the proportion of oil to water or by using ‘depressants’. For instance, in the case of an ore containing zinc sulphide and lead sulphide, the depressant used is sodium cyanide. It selectively prevents zinc sulphide from coming to the froth but allows lead sulphide to come with the froth

Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

∆ f G ∘ of Cu 2 S is more than that of hydrogen sulphide and carbon disulphide CS 2 . Therefore, coke and H 2 will not be able to reduce Cu 2 S . Whereas ∆ f G ∘ of Cu 2 O is lower than carbon monoxide CO . Therefore, C can reduce copper (I) oxide to copper. C s + Cu 2 O s → 2 Cu s + CO g Therefore, it is more difficult to extract copper from copper pyrites than it is to extract from its oxide ore.

What is blister copper? Why is it so called?

Blistered copper is the metallic copper of a black blistered surface, being the product of converting copper matte and having 98.5-99.5% purity. During the process of extraction of Cu from Cu 2 O , the solidified copper obtained has a blistered appearance due to the sulfur dioxide gas evolution and so it is called blister copper.

E M B I B E

Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 28

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Explain zone refining.

Important Questions on General Principles of Metallurgy

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12th Andhra Pradesh Board

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Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 29

Write down the chemical reactions taking place in the extraction of zinc from zinc blende.

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12th Andhra Pradesh Board

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Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 30

Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.

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12th Andhra Pradesh Board

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Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 31

How is alumina separated from silica in a bauxite ore associated with silica? Give equations.

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Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 32

Giving examples, differentiate between ‘roasting’ and ‘calcination’.

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12th Andhra Pradesh Board

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Intermediate Second Year Chemistry>Chapter 5 - General Principles of Metallurgy>Questions>Q 33

The value of $∆_{f} G^{ο}$ for the formation of ${Cr}_{2} O_{3}$ is $- 540 kJ {mol}^{- 1}$ and that of ${Al}_{2} O_{3}$ is $- 827 k J$ ${m o l}^{- 1}$ . Is the reduction of ${C r}_{2} O_{3}$ possible with $A l$ ?