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Half-cell potential?

  1. Apr 20, 2010 #1
    Half-cell potential???

    According to an online chemistry website ( www.chem1.com)
    If the half-cell potential for Zn/Zn+ electrode is defined as the potential difference between a piece of metallic zinc and the solution when the reaction Zn2+ + 2e- -> Zn (s) takes place.

    That is E cell = V metal - V solution

    What does this means?

    Is the metal referring to the electrode and the solution referring to the Zn2+???

    If it is so, then why do half cells with higher potential difference undergo reduction more readily than half cells with lower potential difference?

    I mean the potential difference is supposed to be associated with positive charges, right?

    So if one thing has higher potential, then positive charges would want to move to another thing with fewer amount of positive charges.

    That, in reality, means that the e- would flow from Ag+ to Ag.

    Which is not the usual case???

    Could anyone help me with this?

    I understand that in the activity series,
    we're comparing the performance of each species to those of Hydrogen, so
    the higher the potential, the better electron acceptor it will be.

    But what about this potential thingy??

    Thanks!
     
  2. jcsd
  3. Apr 21, 2010 #2
    Re: Half-cell potential???

    Yes, the solid is the electrode and the Zn2+ is the solution. The reaction you wrote out is a reduction half reaction, and so you would be looking at the reduction potential. This will be positive because the standard hydrogen cell is defined as the zero for these numbers. Basically it's only positive in relation to the SHE, but then again, I'm not exactly sure if this is what you were asking.

    Also be careful with using the word charge. We're dealing with oxidation numbers here, not formal charge.
     
  4. Apr 21, 2010 #3
    Re: Half-cell potential???

    Thank you for your reply. :D

    That's not my question tho
    but i'll think abt it more and post some more questions
    may be i'm confusing myself :(
     
  5. Apr 21, 2010 #4
    Re: Half-cell potential???

    Let's break this down; how familiar are you with redox reactions? Are you just starting to learn about them? It seems like you're not looking at the cell as a whole, which consists of an oxidation AND a reduction. The direction in which each half reaction proceeds is relative to the potential

    Does your question come from a specific example? If so, it would probably help to post all the information you're looking at, and which parts you don't understand.
     
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