Boiling point and vapor pressure

**Does a liquid having higher vapor pressure have a lower boiling point?**
I think so because I read in wikipedia that, "A substance with a high vapor pressure at normal temperatures is often referred to as volatile." A volatile liquid has lower boiling point.




Not necessarily. The vapor pressure of a liquid (or solid) is the pressure of the vapor in equilibrium with its condensed phase in a closed system. The boiling point of a liquid at a given pressure is the temperature at which the vapor pressure is equal to the given pressure. This means the vapor pressure is a function of the temperature,
$ P^\* = f(T) $, and the boiling point is a function of the pressure, $ T\_{bp} = f(P) $. 


So your question is a bit vague. In general, yes, liquids with higher vapor pressures will have lower boiling points. In any first year chemical engineering course, students are introduced to the [Antoine Equation](https://en.wikipedia.org/wiki/Antoine_equation), an emperical relation between vapor pressure and temperature. Plotting the Antoine equation for a set of liquids lets one visualize the relationship between vapor pressure and temperature very quickly; these plots are called Cox charts. For example, examine the Cox chart below:
[![enter image description here](https://i.stack.imgur.com/5VOpf.png)](https://i.stack.imgur.com/5VOpf.png)
Now look at the relationship between ethanol and benzene. At 50 F, benzene has a higher vapor pressure than ethanol. At pressures below ~10 psi, the general trend holds and benzene has a lower boiling point. However, the lines for benzene and ethanol cross at ~10 psi, so above ~10 psi benzene actually has a *higher* boiling point than ethanol.


So in general, **yes, liquids with higher vapor pressures will have lower boiling points.** However, the question is vague and exceptions do exist. 


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Yes, the higher the vapor pressure the more volatile it is and the lower the **normal** boiling point.


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