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Need help. With Thermo

  1. Sep 9, 2012 #1
    Hi, I have my exam in a couple of weeks. And I get the jist of it. However their is one question that I am completly stuck on. Any help would be appreciated.

    Looking over a last years practise text for exam and im having trouble with this.

    Cu(s) → Cu+(aq) + e ΔH = 602 kJ mol-1
    Cu(s) → Cu2+(aq) + 2e ΔH = 795 kJ mol-1
    Work out the Heat of Reaction for the following equation and comment on
    the expected stabilities of Cu+ and Cu2+ ions as predicted from your
    spdf answers in (d).

    2Cu+(aq) → Cu + Cu2+(aq) ΔrH = ????
     
  2. jcsd
  3. Sep 9, 2012 #2

    AGNuke

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    Gold Member

    Try to break it into two equations. Cu+ to Cu2+ and Cu+ to Cu.

    For the first reaction, you can find its ΔH by subtracting the equations given in data. ΔH would be 193 KJmol-1
     
  4. Sep 13, 2012 #3
    Alternative approach, probably simpler:

    The problem you are having is that you do not have a half-reaction connecting Cu(+) and Cu(2+)

    So why not reduce both mole of Cu(+) to Cu, and couple it with oxidizing one mole of Cu all the way to Cu(2+)? That will balance the electrons, and produce the exact overall effect that you are wanting.
     
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