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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: will_L on May 10, 2012, 10:31:48 AM

Title: how to measure the standard electrode of cl2 with reference to standard hydrogen
Post by: will_L on May 10, 2012, 10:31:48 AM
how to draw the cell diagram of cl2.

Given e.m.f of the cell at standard conditions is +1.36v

reactions at the electrodes are: H(g) = (H+)(aq) + e

                                     and  Cl2(g) + (2e-) = (2Cl-)(aq)

giving an overall cell reaction :  Cl2(g) + H2(g) = (2Cl-)(aq) + (2H+)(aq)

Title: Re: how to measure the standard electrode of cl2 with reference to standard hydrogen
Post by: ramboacid on May 10, 2012, 12:28:49 PM
I would guess that you would use platinum electrodes in both of the cells.
Pt|H2, H+||Cl2, Cl-|Pt

http://en.wikipedia.org/wiki/Standard_hydrogen_electrode
Title: Re: how to measure the standard electrode of cl2 with reference to standard hydrogen
Post by: will_L on May 10, 2012, 06:53:10 PM
yeah, but why is it Cl2(g) beside the salt bridge(//) instead of Cl- ? i thot the ions suppose to be next to the salt bridge.
Title: Re: how to measure the standard electrode of cl2 with reference to standard hydrogen
Post by: ramboacid on May 10, 2012, 07:42:38 PM
Quote
yeah, but why is it Cl2(g) beside the salt bridge(//) instead of Cl- ? i thot the ions suppose to be next to the salt bridge.
I wrote the ions by the platinum electrode because that is where reduction occurs, at the cathode. The Cl2 is reduced to Cl- ions at the cathode and H2 is oxidized to H+ at the anode.

I'm not very familiar with line notation for galvanic cells, so my notation might be wrong. I wrote it so that you could "read" the reaction from left to right (H2 is oxidized to H+ and Cl2 is reduced to Cl-).
Title: Re: how to measure the standard electrode of cl2 with reference to standard hydrogen
Post by: will_L on May 10, 2012, 08:02:23 PM
it is correct, cl2(g) and cl- shud be seen as a whole. thanks a lot.