1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Calculating equilibrium constant rules

  1. May 13, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the eq. constant for the reaction

    CH3COOH (aq) + NO2- (aq) = CH3COO- (aq) + HNO2 (aq)

    3. The attempt at a solution

    I find Ka for the reaction CH3COOH = CH3COO- + H+ and Kb for the reaction NO2- + H+ = HNO2

    But what are the rules then? I try multiplying the constants, but this does not give the correct answer.
  2. jcsd
  3. May 13, 2008 #2
    write the K expression for this equilibrium

    then compare it to the Ka expressions for both CH3CO2H AND HNO2
  4. May 13, 2008 #3
    I managed to find the correct solution by multiplying Ka1 and the 1/Ka2. Is 1/Ka2 the same av Kb?
  5. May 14, 2008 #4


    User Avatar

    Staff: Mentor

  6. May 14, 2008 #5
    Did you just happen to work out the numbers and find the right answer or did you see that rearranging the Ka expressions for the acids gave Ka(CH3CO2)/Ka(HNO2) which was equal to the K expression for the original equilibrium?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook