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Homework Help: Equilibrium of reactions - which direction is favored?

  1. Apr 27, 2008 #1
    1. The problem statement, all variables and given/known data

    Is it the same to say the products are favour and the forward reaction is favoured. Or can the reverse reaction be favoured but the products be favoured. For example, the equilibrium constant is >1 so by definition the products are favoured, but if a system has excess products and the reverse reaction is favoured, then??? Im confused.
  2. jcsd
  3. Apr 28, 2008 #2
    That was one of the more confusingly phrased questions i've read.

    As to your initial question, it is the same to say the products are favored or to say the forward reaction is favored. If the Equi constant is > 1, then the system doesn't have excess products (excess meaning enough to stop the reaction).
    Perhaps the semantics of excess is whats confusing you?
    Depending on the reaction you can have a hell-of-a-lot of products and still be favoring a forward reaction.

    Hope that helps.
  4. Apr 28, 2008 #3
    I don't understand what you mean by "excess meaning enough to stop the reaction". I'll try to give you a better example of what I am asking.

    Say you are given a question and you are told that the equilibrium constant is 4. You are then told to find out if the reaction is in equilibrium, so you calculate it only to find that the equilibrium constant you calculated was 9, so you're obviously not in equilibrium and you have excess products (meaning more products than is needed to be in equilibrium). Wouldn't the reverse reaction be favoured in this case because more reactants have to be made to reach the equilibrium constant 4?
  5. Apr 28, 2008 #4
    If your "product" is in excess, giving you the higher than expected Keq value, then the reverse reaction will proceed more quickly, to respond to the stress on the equilibrium system.
  6. Apr 28, 2008 #5
    Thanks, so even if the reverse reaction is proceeding more quickly, the forward can be favoured as depicted by the Keq value > 1?
  7. Apr 28, 2008 #6
    No. If the forward reaction is favored, then the forward reaction is going faster, and the products are favored - meaning more products are going to be produced.
  8. Apr 28, 2008 #7
    That doesn't make sense with the definition then. Because in my textbook it defines that if the equilibrium constant is greater than one, then the forward reaction is favoured. Couldn't your reverse reaction be proceeding faster while having a equilibrium constant greater than one?
  9. Apr 29, 2008 #8
    No, you cant. The equi constant tells you which direction the reaction is going ( / is going faster. Which direction the reaction is going, tells you if the products or the reactants are favored (i.e. forward = reactants favored).
  10. Apr 29, 2008 #9


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    Note that the equilibrium deals with the rate constants and not the actual rates - this aspect is very important.
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