(B) The reduction of $H^+$ ions at a $Hg$ cathode requires a higher overpotential (voltage) compared to a $Pt$ cathode. Due to this high overpotential

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More voltage is required to reduce $H^+$ ions at a $Hg$ cathode than at a $Pt$ cathode.

(B) The reduction of $H^+$ ions at a $Hg$ cathode requires a higher overpotential (voltage) compared to a $Pt$ cathode. Due to this high overpotential,the reduction of $Na^+$ ions to $Na$ metal becomes more favorable at the $Hg$ cathode,which then reacts with $Hg$ to form sodium amalgam $(Na-Hg)$.

Class 12 Chemistry Electrochemistry Electrolytes and Electrolysis

Medium

During the electrolysis of $NaCl$ solution,$H_2$ gas is liberated at the cathode when a $Pt$ electrode is used,whereas sodium amalgam is formed when a $Hg$ cathode is used. What is the reason for this?

A
$Hg$ is more inert than $Pt$.
B
More voltage is required to reduce $H^+$ ions at a $Hg$ cathode than at a $Pt$ cathode.
C
$Na$ dissolves in $Hg$ while it does not dissolve in $Pt$.
D
The concentration of $H^+$ is higher when a $Pt$ electrode is used.