Given two boiling temperatures and pressures, how can I find the latent heat?

Question

I am given the fact that at a certain pressure a liquid boils at a corresponding temperature, at a different pressure it boils at a different temperature, and then I am asked to find the latent heat from that information, how do I do that?

Answer 1

The Clausius–Clapeyron equation:

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

relates $\frac {dP}{dT}$ to the latent heat and volume change. If the two temperatures you have are fairly close you can approximate $\frac {dP}{dT}$ then all you have to do is work out the volume change and you can calculate the latent heat.