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Explaining why some reactions are spontaneous at certain temperatures

  1. Aug 24, 2011 #1
    On an exam I got this question:
    [PLAIN]http://img849.imageshack.us/img849/5732/spontaneity.png [Broken]
    but at the time I had no idea how to answer it. I still don't really know if I can answer it. I can explain it mathematically with the equation: ΔG = ΔH - TΔS seeing as a spontaneous reaction requires a negative change in G and therefore if the sign of ΔH and ΔS are different then temperature will be a determining factor as to whether or not ΔG will be negative. I have no idea what I would need to plot on a graph though. As for examples of reactions of each type I suppose I needed to have a few example reactions memorised.
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Aug 24, 2011 #2


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    How about plotting ΔH, -TΔS, and their sum?
  4. Aug 24, 2011 #3
    Oh yeah didn't think of that. I could also plot T vs. their sum.
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