# Dissociation constant as function of T,p.

1. Jan 8, 2015

### prehisto

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.
alpha=1/(sqrt(1+4k))
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. Jan 8, 2015

### Bystander

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?

3. Jan 8, 2015

### prehisto

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.

4. Jan 10, 2015

### Bystander

You need enthalpy and heat capacity data (or estimates) for the reaction to examine temperature dependence.

5. Jan 10, 2015

### prehisto

I got it!
it is possible to get relation by using reaction heat
Q=RT^2 d/dT (ln K)