[tou]

Hi

I have 2 questions - concerning the electrodes in voltaic and electrolytic cells, and the electrode potentials.

So oxidation occurs always at the anode right? But in voltaic cells it is the negative electrode and in electrolytic cells it is the positive electrode. Where does this naming come from / what is the convention?
I get that in electrolytic cells, there is an external source of energy - so the electrode connected to the negative end is where reduction occurs, it can supply electrons and thus reduction occurs - or thats how I understood it.
In voltaic cells - is it related to the reactivity series? Is that why the electrodes are negative or positive in the first place? For example Zn is oxidized and e- move to Cu because Zn has the more negative electrode potential? Whereas in an electrolytic cell - the electrodes are inert...?

Then I have another question about the electrode potentials. When a half cell is attached to a standard hydrogen cell, and the e- move from the H cell to the standard cell - the value is is positive - why is that?

Thanks a lot!

[cliverlong]

Yes, the definition of anode and cathode can be confusing. I think you have essentially the right ideas.

From

http://en.wikipedia.org/wiki/Electrochemistry#Oxidation_and_reduction

I quote

The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place.
 
Also the following thread on this forum might help to distinguish electrolystic and electrochemical cells

http://www.chemicalforums.com/index.php?topic=26468.msg100222;topicseen#msg100222

Clive

[leve]

The answer to your first question is in the direction of the electrons and the source and receiver of the electrons

For your second question, the electron moves from the standard hydrogen electrode (SHE), or the anode to the cathode. Remember, what is the value of the standard cell potential for SHE?