Question

In the extraction of chlorine by electrolysis of brine_________.
A. oxidation of `Cl^(-)` ion to chlorine gas occures
B. reduction of `Cl^(-)` ion to chlorine gas occures
C. for overall reaction `Delta G ^( ө )` has negative value
D. a displacement reaction takes place

Answer 1

Correct Answer - A
(a) Following reaction takes place in the extraction of chlorine by electrolysis
`2H_(2)O(l)+2Cl^(-)(aq) to H_(2)(g)+Cl_(2)(g)+2OH^(-)(aq)`
From the above reaction it is very clear that the oxidation of `Cl^(-)` ion to chlorine gas occurs. Thus, option (a) is the correct answer.
`Delta^(@)G` for this reaction is +422J. Therefore, thermodynamically reaction is not feasible. We know that.
`Delta^(@)G=-nFE^(@)`
By using this equation value of `E^(@)` can be calculated. Thus,
`E^(@)=-(DeltaG^(@))/(nF)=-2.2V`
Therefore, for the occurance of this reaction, external potential (emf) greater than 2.2V is required. Due to this fact ( c) is not the correct option.