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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: sajib_mostofa on November 09, 2010, 12:08:16 pm

Title: Electrolysis Q
Post by: sajib_mostofa on November 09, 2010, 12:08:16 pm: Magnesium metal is produced by passing a current through molten $MgCl$ ₂.

a) Write the equations for the reactions occuring at the anode and cathode.

I figured that the cathode reaction would be $Mg^{2+}+2e^{-}\rightarrow Mg$ as Mg is being formed. But why is the anode reaction
$2Cl^{-}\rightarrow Cl_{2} + 2e^{-}$ ?
Title: Re: Electrolysis Q
Post by: fady_22 on November 09, 2010, 12:11:57 pm: It's a molten solution, and there is no water present.
Title: Re: Electrolysis Q
Post by: 3Xamz on November 09, 2010, 12:12:45 pm: There's only Mg and Cl ions in the molten MgCl2.
I would presume if Mg+2 is being reduced, Cl- must be oxidized?
Hence that equation.

That's my two cents worth ><
Title: Re: Electrolysis Q
Post by: sajib_mostofa on November 09, 2010, 12:14:48 pm: Quote from: fady_22 on November 09, 2010, 12:11:57 pm
It's a molten solution, and there is no water present.

So whenever something is in molten form, water will never be present?
Title: Re: Electrolysis Q
Post by: jasoN- on November 09, 2010, 12:15:58 pm: yes definitely. this is the key point in molten compounds.
Anything under water (as an oxidant) cannot be reduced unless it is in molten form (ie. pure liquid)
Title: Re: Electrolysis Q
Post by: fady_22 on November 09, 2010, 12:16:09 pm: Quote from: sajib_mostofa on November 09, 2010, 12:14:48 pm
Quote from: fady_22 on November 09, 2010, 12:11:57 pm
It's a molten solution, and there is no water present.

So whenever something is in molten form, water will never be present?

Yes. Molten means that the MgCl2 is heated to the point of melting (in liquid form). So there is no water.
Title: Re: Electrolysis Q
Post by: sajib_mostofa on November 09, 2010, 12:17:49 pm: Cheers for that guys
Title: Re: Electrolysis Q
Post by: 3Xamz on November 09, 2010, 12:23:57 pm: Yup, you should know that because its fundamental to the production of some everyday chemical that is more than likely to assessed in the upcoming exam. Good luck! :)
Title: Re: Electrolysis Q
Post by: sajib_mostofa on November 09, 2010, 12:33:11 pm: Quote from: 3Xamz on November 09, 2010, 12:23:57 pm
Yup, you should know that because its fundamental to the production of some everyday chemical that is more than likely to assessed in the upcoming exam. Good luck! :)

Haha cheers man. Good luck to you too.