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Offline cheungcheung

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« on: 23/06/2004 13:54:43 »
For sodium chloridei n water
How does hydrogen ion gain an electron during electrolysis(when NaCl in water)?
Is that the electron is from chloride ion and passing through the carbon electrode and combine with hydrogen ion?


Offline Ylide

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Re: electron
« Reply #1 on: 24/06/2004 02:15:17 »
Electrolysis of NaCl in water will yield chlorine gas.  Since the chlorine ions are negative (anions), they each have 8 (1 extra) electrons in their valence shell.  Diatomic chlorine gas has 14 total electrons in the outer shell, so every molecule of chlorine that is formed yields 2 free electrons to be picked up be sodium ions or, if present, hydrogen ions.

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Offline chris

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Re: electron
« Reply #2 on: 29/06/2004 05:30:09 »
Yes, in aqueous solution pairs of hydrogen ions (which bear a positive charge) migrate to the negative electrode (the cathode) where they acquire 2 electrons and form a molecule of hydrogen (H2). The electrons are essentially derived from pairs of chloride ions (Cl-) which migrate to the anode (+ electrode), donate 2 electrons and combine covalently to form gaseous chlorine (Cl2) which bubbles out of the solution.

I'm not sure whether any oxygen is produced also - cannabinoid might be able to help me on that point.

Sodium ions will also migrate in the solution, but I think they require too much energy to acquire an electron to form metallic sodium - and besides, if this did happen they would instantly react with the surrounding water to yield more hydrogen gas, sodium ions and hydroxide ions.

However, electrolysis of molten sodium chloride is a different matter. Under these conditions (using large carbon anodes and a mercury cathode) chlorine gas is collected at the anode, whilst metallic sodium forms an amalgam with the liquid mercury cathode. In a separate chamber the mercury / sodium amalgam is mixed with water. The sodium reacts with the water producing hydrogen gas and sodium hydroxide solution, both of which are useful products. The mercury is meanwhile recycled back to the eletrolysis vessel.


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The Naked Scientists Forum

Re: electron
« Reply #2 on: 29/06/2004 05:30:09 »


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