1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Homework Help: Dissociation constant as function of T,p.

  1. Jan 8, 2015 #1
    1. The problem statement, all variables and given/known data
    For given general reaction 2A<->A2 the affinity constant is known k(T)=1.7 10-4 mol/cm3 (t=18 C) Find dissociation (constant) level in normal pressure.
    2. Relevant equations
    So i solved it - found the general solution for dissociation constant.
    Now i have some quaestions,So first of all where do i factor in the pressure?
    Like this alpha=1/(sqrt(1+4 p k(T))) and if yes what kind of units would be correct to use?

    More importantly If i need to calculate the dissociation constant for the same reaction but only in different temperature, what should i do then ?

    Looking forward to hearing from you guys!

    3. The attempt at a solution
  2. jcsd
  3. Jan 8, 2015 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    PTotal = ∑Pi, where Pi are the partial pressures of all species present. Conversely, mole fraction x PTotal is the partial pressure of a selected species. Units obvious enough to you with that information?
  4. Jan 8, 2015 #3
    yes, i think units are clear now ,thanks :)

    But still,not clear what to do with different temperature i know that k(t)=Exp(a),where a is function form chemical potential maybe its possible to calculate in this way. but its seems irrational.
  5. Jan 10, 2015 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You need enthalpy and heat capacity data (or estimates) for the reaction to examine temperature dependence.
  6. Jan 10, 2015 #5
    I got it!
    it is possible to get relation by using reaction heat
    Q=RT^2 d/dT (ln K)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted