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CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar 2 Mark Questions 2021

Published on: 25/05/2021

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Std: 12th Standard CBSE - Chemistry

chapter: - NCERT Exemplers

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Questions:

Generic 2

5 x 2 = 10

How is copper extracted from a low grade ore of it?

How are metals used as semiconductors refined?What is the principle of the method used?

What is the role of flux in metallurgical processes?

What should be the consideration during extraction of metals by electrochemical method?

Which method is used for refining Zr and Ti? Explain with equation.

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Answers Key:

Generic 2

5 x 2 = 10

Extraction of Copper from low-grade ores and scraps: It is extracted by hydrometallurgy. It is carried out in two steps:
1. Leaching: Low-grade copper ores and scraps are leached by using acid or bacteria.
2. Reduction: The solution containing copper ions is treated with H₂. \({ Cu }^{ 2+ }(aq)+{ H }_{ 2 }(g)\longrightarrow Cu(s)+{ 2H }^{ + }(aq)\)

Semiconducting metal is produced by zone refining method which is based on the principle that th~ impurities are more soluble in melt than in the solid state of metals

Flux is used for making the molten mass more conducting.

During extraction of metals by electrochemical method, the following are considered so the at proper precautions can be taken:
(i) reactivity of metal produced.
(ii) suitability of electrodes

van Arkel method is used for refining Zr and Ti. In this method, impure metal is heated with iodine which decomposes to give pure metal and iodine is recovered.
\(Zr+{ 2I }_{ 2 }\longrightarrow { ZrI }_{ 4 }\)
\({ ZrI }_{ 4 }\overset { 1800K }{ \longrightarrow } Zr+{ 2I }_{ 2 }\)