# Homework Help: Phase Boundary between mono and diatomic gases

1. Jan 13, 2016

### samjohnny

1. The problem statement, all variables and given/known data

Consider a gas (note: treat as ideal) that has phase coexistence between diatomic and monatomic forms at $T_0$ and $P_0$. Compute the equation for the P,T phase boundary between monatomic and diatomic gases.

2. Relevant equations

$u_v (V,T) = \frac{5}{2} RT - \frac{a}{v} - u_b$

$u_i (V,T) = \frac{5}{2} RT - u_b$

Where $u_b$ is the energy holding atoms together in a diatomic gas.
And $u_i$ and $u_v$ are the molar energies of ideal and van der waals diatomic gases respectively.

3. The attempt at a solution

I'm assuming that the equation for the phase boundary has something to do with computing $\frac{dP}{dT}$. So the first thing that springs to mind is the Clausius Clapeyron, however, how to relate that to the equations given for the internal energies I'm not sure.

2. Jan 18, 2016