Equilibrium constant

  1. 1. The problem statement, all variables and given/known data
    The total pressure of gases in equilibrium with solid sodium hydrogen carbonate at 110.0 degrees C is 1.648 atm, corresponding to the reaction

    2NaHCO3(s) <--> Na2CO3(s) + H2O(g) + CO2(g)

    a) Calculate the value of the equilibrium constant at 110.0 degrees C.



    3. The attempt at a solution
    I don't know how to begin this because I don't know how to find the initial partial pressure of sodium hydrogen carbonate. How am I supposed to use P total at equilibrium in this problem?
     
  2. jcsd
  3. The solid sodium bicarbonate has negligible vapor pressure at 110 degrees C. We usually treat solids as constants, which we then divide out of the equilibrium constant; the only terms you should be left with in your expression for K are from gaseous water and gaseous carbon dioxide.

    This approach for dealing with solids holds true in general, unless the equilibrium being studied occurs in a solid solution (e.g., molten rock.)
     
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