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What makes electron flow in an electrochemical cell

  1. Jul 3, 2012 #1
    So, here is my question we know about an electrochemical cell in which when zink rod and copper rod are dipped in there respective solutions the electron flow from zink rod to cu .... but what makes those electron to flow .... here comes the answer the potential difference did that ... please explain in detail :confused:
  2. jcsd
  3. Jul 3, 2012 #2


    Staff: Mentor

  4. Jul 3, 2012 #3
    no it did`t help
  5. Jul 3, 2012 #4
    The potential difference doesn't make the eletrons flow in the solution, because:

    1. there are no free electrons in the solutions.

    2. The potential difference would make the electrons flow from the negative rod to the positive rod This is the wrong direction, because the electrons have to go through the wire from the negative to the positive rod, not through the solution.

    What's happening in a battery that there's a chemical reaction at the negative rod that produces electrons, and a reaction at the positive rod that consumes them.

    If you put copper and zinc in an acid, you get Zn -> Zn(2+) + 2e at the negative side, and 2H(+) + 2e -> H2 at the positive side.

    If you don't connect the cell to anything, the reaction will proceed until you get a potential difference of about 0.9V. At this potential the reactions would cost energy and will no longer occur spontaneously.

    If you connect the positive and the negative side, the electrons can move from the positive side to the negative side, the potential difference will become less, and the reactions will continue.

    The current that moves in the solution are the H(+) ions, and these will move against the electric field towards the positive rod. This can happen because of diffision. The ions bounce around randomly, and so there can be a net movement from a higher concentration towards a lower concentration around the positive rod, where the reaction has depleted them.
    The Zn(2+) also have to diffuse away in the same way from the negative rod, even tough it attracts them

    Higher temperatures increase diffusion, and so will increase the potential difference of a cell slightly, and decrease the internal resistance a lot. This is why car batteries don't work as well in the winter as in the summer.
  6. Jul 4, 2012 #5
    1...if i take only one part of cell .... will the reaction Zn ----> Zn(2+) + 2e take place??
    2...if i just put the zn rod in zinc solution will the rod melt ???
    3...if i will put a zinc rod outside a beaker containing copper sulphate solution and connect the rod and solution with a wire will any reation take place???
    please explain
  7. Jul 4, 2012 #6
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