A) Hg is more inert than\[Pt\]
B) more voltage is required to reduce \[{{H}^{+}}\] at \[Hg\] than at\[Pt\]
C) \[Na\] is dissolved in \[Hg\] while it does not dissolved in\[Pt\]
D) concentration of \[{{H}^{+}}\] ions is larger when \[Pt\] electrode is taken
Correct Answer: B
Solution :
Sodium chloride in water dissociates as \[NaClN{{a}^{+}}+C{{l}^{-}}\] \[{{H}_{2}}O{{H}^{+}}+O{{H}^{-}}\] when electric current is passed through this solution using platinum electrode, \[N{{a}^{+}}\] and \[{{H}^{+}}\] move towards cathode. Whereas \[C{{l}^{-}}\] and \[O{{H}^{-}}\] ions move towards anode. At cathode \[{{H}^{+}}+{{e}^{-}}\xrightarrow{{}}H\] \[H+H\xrightarrow{{}}{{H}_{2}}\] At anode \[C{{l}^{-}}-{{e}^{-}}\xrightarrow{{}}Cl\] \[Cl+Cl\xrightarrow{{}}C{{l}_{2}}\] If mercury is used as cathode, \[{{H}^{+}}\] ions are not discharged at mercury cathode because mercury has a high hydrogen over voltage.\[N{{a}^{+}}\]ions are discharged at cathode in preference of \[{{H}^{+}}\] ions yielding sodium, which dissolves in mercury to form sodium amalgam.
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