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Negative entropy value for F- (aq) and OH-(aq)?

  1. Apr 28, 2010 #1
    I'm currently studying thermodynamics, and while looking through the chart of [tex]\Delta[/tex] H[tex]\circ[/tex], S[tex]\circ[/tex], and [tex]\Delta[/tex] G[tex]\circ[/tex] values for 200+ substances. Out of these, I noticed that two (F- (aq) and OH- (aq) have a negative S[tex]\circ[/tex] value. How can a single ion have a negative entropy? I understand that irreversible rxns and rxns with more moles of product than reactants have a negative S[tex]\circ[/tex] value, but I am having trouble seeing a negative entropy value for an ion. And why just F- and OH-? What makes them special? Electronegative? (For F- at least..)?

  2. jcsd
  3. Apr 28, 2010 #2
    Your table most likely lists values for the standard formation enthalpies and entropies. A negative So value just means that going from F2(g) to F-(aq) involves a decrease of entropy.
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