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Electroplating, anode and cathode help.

  1. Apr 19, 2013 #1

    Cee

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    I'm just having trouble understanding, I get the gist of it though.
    This is what I know in a electrolytic cell (I may be wrong):
    The cathode is negative, anode is positive and the current travels from the cathode to anode right?

    So during electroplating, the anode is the electrode being deposited to... but if it's the anode, that means oxidation occurs and loses electrons. In the end, how does the anode have a larger mass? I just can't get my head around the oxidation and reduction.

    I have done my fair share of research and googling but I'm still confused. Especially this:

    http://img526.imageshack.us/img526/6060/elctro.png [Broken]

    Unless the diagram is absolutely wrong, it looks to me as if the electron start from the left (spoon) and electroplates the silver but that's not how they explain it...

    Help would be greatly appreciated, thank you.
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Apr 19, 2013 #2

    NascentOxygen

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    Staff: Mentor

    Hi Cee. You have to keep your wits about you in electrochemistry! Unless you are already given the terms "anode" and "cathode", IMHO It's best not to introduce them because in some cells (e.g., a lead-acid battery) the terms swap when you attach the charger!

    Also, only refer to "current" when discussing the external copper wire conductor. If examining flow of charges in the electrolyte, refer to migration of ions because that's how charge is moved around. (It's wrong to visualize it as electron movement.)

    With those tips out of the way, given the way the battery symbol is depicted we can say current flows from the battery's right hand terminal through the ammeter, and to the block of silver.

    http://physicsforums.bernhardtmediall.netdna-cdn.com/images/icons/icon2.gif [Broken] Remember, due to historical accident, electrical current in a wire is defined to be opposite to the direction that electrons flow!

    This means electrons are emerging from the cell's silver block and flowing through the ammeter to the battery's right side, and ― as is the nature of batteries ― corresponding numbers of electrons emerge from the battery's left side flowing towards the spoon.

    Electrons don't bank up anywhere, so they must be meeting some + ions at the junction of that metal spoon and the solution. That equates to a migration of Ag+ through the electrolyte towards the spoon, and at the spoon's surface these ions gain an electron and deposit out as Ag metal.

    All clear?
     
    Last edited by a moderator: May 6, 2017
  4. Apr 20, 2013 #3

    Borek

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    Staff: Mentor

    During electrolysis silver is deposited at the cathode.
     
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