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Why does the equilibrium constant vary only with temperature?

  1. Oct 24, 2006 #1
    why does the equilibrium constant vary only with temperature?

    and why is pure substances like solids and liquids not count toward the equilibirum equation?

    why do you have to have a reference pressure of 1 atm? (i know this is to take away the units but does this hav a logical function other than that? how does this affect the equation?)

    can noble gases affect the equilibrium? (i think it shouldnt since the partial pressure of the original reactants would still be the same)
  2. jcsd
  3. Oct 27, 2006 #2


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    The policy here at PF is that you show your approach to the question before any of us are allowed to help you. However, the questions you have asked in particular are commonly asked by students outside their homework endeavors and thus I shall offer an brief explanation. An appropriate explanation for all of these questions entails several mathematical derivations and the related assumptions, all of this can be found in a standard Physical Chemistry text e.g. Physical Chemistry by Atkins.

    Your text should offer a short explanation on why the equilibrium constants of some reactions in water is altered by temperature, in short, all of it stems from the relative changes in the forward and reverse rate constants for a simple reaction mechanism. Also, the rate constants are thermodynamically based, as it is associated with the activations energies for the forward and reverse reactions respectively.

    Liquids and solids technically do count, to a very small degree, towards the rate equations, however they are mathematically insignificant in influencing the rate parameters.

    1 atm is the standard condition.

    The presence of any gas would affect the collision frequency of the analyte and thus would affect the rate dynamics.
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