In electrolysis of NaCl when Pt electrode is taken then H _2 is liberated at cathode while with Hg cathode it forms sodium amalgam :

NEET 2002 Chemistry question

In electrolysis of NaCl when Pt electrode is taken then is liberated at cathode while with Hg cathode it forms sodium amalgam :

(1)Hg is more inert than Pt
(2)More voltage is required to reduce at Hg than at PtCorrect
(3)Na is dissolved in Hg while it does not dissolve in Pt
(4)Conc. of ions is larger when Pt electrode is taken

Answer: (2)

Solution

At a Pt cathode, (from water) is reduced in preference to because its reduction potential is much higher, so is liberated. At a mercury cathode, hydrogen has a very high overpotential: much extra voltage is needed to discharge (as ) on Hg. Under these

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Question ID VK-089003