I've produced experimental data over how the boiling point of water varies with pressure and temperature and plotted this in a PT graph. I would like to verify my results using theory. The Clausius-Clapeyron equation appears to be exactly what I want. I did manage to find a table over heat of vaporization depending on pressure, so that this version of Clausius-Clapeyron is almost applicable:

$$ \frac{dP}{dT}=\frac{L}{T\Delta v} $$

However, I don't have any values for $\Delta v$. So what are my options? Is there some approximation I can make to find the value for $\Delta v$ or is there another version of Clausius-Clapeyron I can use to find $\frac{dP}{dT}$ using freely available tables? Or would someone suggest another way of verifying my results?


The usual approximation is to disregard liquid volume against vapor volume, and to consider the latter to be that of an ideal gas, so you get $\Delta v = RT - 0 = RT$ and so

$$ \frac{dP}{dT}=\frac{L}{RT^2} $$

If you simply want to check your results, there are also plenty of available resources on-line with boiling points for water as a function of pressure, such as this.


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