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General Principles And Processes Of Isolation Of Elements

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Question
CBSEENCH12010892
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During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’ These are

  • Sn and Ag

  • Pb and Zn

  • Ag and Au

  • Fe and Ni

Solution

C.

Ag and Au

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Question
CBSEENCH12010954
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Excess of KI reacts with CuSO4 solution and then Na2S2O3 solution is added to it. Which of the statements is incorrect for this reaction?

  • Cu2I2 is reduced

  • Evolved I2 is reduced

  • Na2S2O3 is oxidized

  • CuI2 is formed

Solution

D.

CuI2 is formed

CuSO4 + 2KI → Cul2 + I2 
Thus Cul2 is not formed.

Question
CBSEENCH12010897
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Heating mixture of Cu2O and Cu2S will give

  • Cu + SO2

  • Cu + SO3

  • CuO + CuS

  • Cu2SO3

Solution

A.

Cu + SO2

2Cu2O + Cu2S → 6Cu + SO2

Question
CBSEENCH12010634
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In the context of the Hall-Heroult process for the extraction of Al, which of the following statements is false?

  • CO and CO2 are produced in this process

  • Al2O3 is mixed with CaF2 which lowers the melting point of the mixture and brings conductivity

  • Al3+ is reduced at the cathode to form Al

  • Na3AlF6 serves as the electrolyte

Solution

D.

Na3AlF6 serves as the electrolyte

Question
CBSEENCH12010657
Wired Faculty App

The metal that cannot be obtained by electrolysis of an aqueous solution of its salts is

  • Ag

  • Ca

  • Cu

  • Cr

Solution

C.

Cu

Higher the position of the element in electrochemical series more difficult is the reduction of its cations.
 If Ca2+ (aq) is electrolyzed, water is reduced in preference to it. Hence, It cannot be reduced electrically from their aqueous solution.
Ca2+ (aq) + H2O → Ca2+ +OH- +H2

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