Which one of the following statements is incorrect? a. In the silver plating of

Question

Which one of the following statements is incorrect? a. In the silver plating of a spoon, the spoon is made the cathode. b. In the electrolytic refining of copper the pure copper is made the cathode. C. During the electrolysis of a sodium sulfate solution, hydrogen gas is liberated at the anode. e. During the electrolysis of molten sodium chloride, chlorine gas is liberated at the cathode. 16. Identify the oxidizing agent, the reducing agent, and which chemical species is reduced respectively in the following reaction:

Explanation / Answer

15) Incorrect statement = e

In the electrolysis of molten NaCl , chlorine gas is liberated at anode.

In this reaction,

at cathode :   2Na+ + 2e- --------------> 2Na (Reduction)

at anode:   2Cl---------------> Cl2 + 2e- (Oxidation)

16) Given reaction is

Cr2O72- + I- + 8H+ ----------> 2Cr3+ + IO3- + 4H2O

In this reaction,

Oxidation number of Cr in   Cr2O72- = +6

   Oxidation number of Cr in   Cr3+ = +3

    Oxidation number of I in I- = -1

    Oxidation number of I in IO3- = +5

Increase in oxidation number = oxidation

decrease in oxidation number = reduction

Hence,

Cr2O72- is reduced to Cr3+ and I- is oxidized to IO3-.

Therefore,

oxidizing agent = Cr2O72-

reducing agent = I-

chemical species reduced = Cr2O72-

  

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