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Homework Help: Understanding Equilibrium Constants With No Denominator

  1. Mar 22, 2009 #1
    Lets say you have something like
    CaSO4 (s) <-----> Ca (aq) + SO4(aq)

    The equilibrium constant would then have no denominator. That makes no sense to me!!!

    K would equal [ Ca ][ SO4 ].

    Wouldn't that then represent a constant amount of moles no matter how much CaSO4 is present?

    Lets say K = 4 in this case
    and [ Ca ] = 2 and [ SO4 ] = 2

    Because K isn't a fraction, there is no way to reach equilibrium by balancing the reactant and products. K would then suggest the maximum molarity for a given solution, no matter how much solid reactant is in the solution.

    That's how I'm interpreting it but it just seems wrong. Can someone clarify for me?

  2. jcsd
  3. Mar 23, 2009 #2


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    The concentration of CaSO4 in solid CaSO4 is a constant. Multiplying the inverse of that constant by [ Ca ][ SO4 ] gives you your K. Sometimes the constant is not shown (like in solubility products).
    Last edited: Mar 23, 2009
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