Electrochemistry - Result Question 40

####39. An aqueous solution of NaCl on electrolysis gives H2(g),Cl2(g) and NaOH according to the reaction.

2Cl(aq)+2H2O2OH(aq)+H2(g)+Cl2(g)

A direct current of 25A with a current efficiency of 62 is passed through 20L of NaCl solution ( 20 by weight). Write down the reactions taking place at the anode and cathode. How long will it take to produce 1kg of Cl2 ? What will be the molarity of the solution with respect to hydroxide ion? (Assume no loss due to evaporation)

(1992, 3M)

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Solution:

  1. At anode

2ClCl2+2e

At cathode 2H2O+2eH2+2OH

1kgCl2=100035.5 equivalent of Cl2=28.17 equivalent

Theoretical electricity requirement =28.17F

Efficiency is only 62

Electricity requirement (experimental)

=28.17×10062F=45.44F 45.44×96500=25t (in second)  t=48.72h

Also, gram equivalent of HOproduced =28.17

Molarity of HO=28.1720=1.4085M



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