# Dissociation constant as function of T,p.

• prehisto

## Homework Statement

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.

## Homework 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!

## The Attempt at a Solution

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?

Bystander said:
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?

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.

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

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

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