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Equilibrium constants

  1. Jun 18, 2008 #1

    ycn

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    Hi, can someone help me on the following question.

    Equilibrium constant=0

    Equilibrium constant=1

    What are the significance of these 2 values? As in, what is happening to the reactants as well as the products in this 2 instances? Thank you!!
     
  2. jcsd
  3. Jun 18, 2008 #2

    Borek

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    Staff: Mentor

    Write any reaction equation (even as simple as A <-> B), write expression for its equilibrium constant. Then it is simple math - think when equilibrium constant can equal 0 and when it can can equal 1, think in terms of values of concentrations of products and reactants.
     
    Last edited: Jun 18, 2008
  4. Jun 19, 2008 #3

    ycn

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    But what do the numbers means?

    Eg. a + b [tex]\Updownarrow[/tex] c + d

    Kc = [c][d]/[a]

    Kc = 1 will mean [c][d] = [a]

    Kc = 0 will mean either [c] is zero or [d] is zero

    1. Is the enthaply change for the reaction zero?
    2. Is there no reaction?
    3. Is the activation energy zero?
     
  5. Jun 20, 2008 #4

    Borek

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    Staff: Mentor

    Let's start with the second case. If you start with a and b - what does it mean if c or d is zero? Think about the reaction stichiometry. If c is zero - what about d? How did a and b changed?
     
  6. Jun 20, 2008 #5

    ycn

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    That means the other product should have zero concentration. Which also means no reaction would have taken place. Oh okok, thanks a lot, really!!

    Then in the case for Kc = 1, amount of reactant is equal to the product. That means half of the reactants have been converted into the product, and the reaction has just reached dynamic equilibrium. So can i say it's just a normal equilibrium reaction. Thanks
     
  7. Jun 20, 2008 #6

    Borek

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    Staff: Mentor

    Sure you can, but it won't hurt to analyse it a little bit further. Think what it does mean when Kc > 1 or Kc < 1. Where the equilibrium lies - on the left, on the right? Kc = 1 doesn't have any special meaning, but it happens to be a border case.



     
    Last edited: Jun 20, 2008
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