Q7 of 26 Page 1

following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:

Na+(aq) + e- →Na(s) E° = -2.71V


H+(aq) + e- → H2 (g) E° = 0.00V


(a)On the basis of their standard reduction electrode potential (E°) value, which reaction is feasible at cathode and why?


(b) why does the cell potential of mercury cell remains constant throughout its life?


The reduction of H+ to 1/2 H2 gas is more feasible at cathode as E° reduction of hydrogen is more than that of sodium. So at cathode reduction of hydrogen will take place.

(b)In the overall reaction of mercury cell, there is no involvement of any ion whise concentration can be changed. And due to absence of that, the mercury cell gives the constant potential of 1.35V throughout its life.


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