I don't understand what causes redox reactions to occur.

  1. For example, on this website http://www.chemguide.co.uk/physical/redoxeqia/combinations.html in the second diagram from the top, it shows that *if a high resistance voltmeter is placed between two pieces of metal, zinc and copper, the zinc metal will accumulate a build up of electrons.* Then when the resistance is relieved, the electrons will necessarily flow to the copper metal, which I understand.

    What I'm confused about is: why do electrons build up on the zinc metal in the first place, and where do the electrons come from?

    Thank ya.
  2. jcsd
  3. Borek

    Staff: Mentor

    This is exactly the same question you can ask for every chemical reaction - why does it go the way it does. Short answer is - because it is thermodynamically favorable. In most cases that means that products have lower energy than reactants (although this is oversimplification).

    From the half reaction - Zn "prefers" to be in the ionic form, and some of the atoms "jump" into solution leaving their electrons in the bulk of the metal.
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