Estimate the latent heat of water

1. May 24, 2015

It's me

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

Try to estimate the latent heat of vaporization of water and nitrogen using the Van der Waals model. What happens?

2. Relevant equations

$$ΔQ=TΔS=L$$

$$S=nR[\ln(\frac{(V−nb)T^{3/2}}{nΦ})+\frac{5}{2}]$$

3. The attempt at a solution

I predict the latent heat of vaporization of water will be wrongly approximated by the Van der Waals model. By looking at the equation for entropy I think the ΔS is going to be zero, so the latent heat would be zero also. But I am not sure if I am looking at the problem in the wrong way.

2. May 25, 2015

BvU

Why would $\Delta S$ be zero ?