Q61 of 136 Page 42

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion : Electrolysis of NaCl solution gives chlorine at anode instead of O2.


Reason : Formation of oxygen at anode requires overvoltage.


In the electrolysis of NaCl solution, Chlorine is produced at anode instead of O2. The two half-cell reactions are:


2Cl-→ Cl2(g) + 2e- E° = -1.36V


2H2O →O2(g) + 4H+ + 4e- E° = -1.23V


Generally, the one with the lower value is preferred but in this case Chlorine is produced at anode. This is because formation of oxygen at anode requires overvoltage.

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59

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion : for weak electrolytes shows a sharp increase when the electrolytic solution is diluted.


Reason : For weak electrolytes degree of dissociation increases with dilution of solution.


 60

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion : Mercury cell does not give steady potential.


Reason : In the cell reaction, ions are not involved in solution.


 62

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion : For measuring resistance of an ionic solution an AC source is used.


Reason : Concentration of ionic solution will change if DC source is used.


 63

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion : Current stops flowing when ECell = 0.


Reason : Equilibrium of the cell reaction is attained.