How do you tell if a compound has a high volatility?
Also can the boiling point of a compound be taken into consideration when determining if a compound has a high volatility?
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This answer is in the same spirit that the question is given, which is to just get an idea about volatility of a compound given its chemical formula. I need to make it clear that there are times when you need to quickly compare two chemical structures in your head and decide which one is more volatile. For that, you can use the below criteria, however, for more rigorous and serious calculations, you need to directly evaluate vapor pressure using known experimental data or precise thermodynamic models.
When comparing two molecules:
1- lower molecular weight leads to higher volatility
2- presence of polar groups usually decreases volatility
3- presence of hydrogen bonding sites significantly decreases volatility
Vapor pressure is the physical property that expresses a compound's volatility at a given temperature, and the enthalpy of vaporization describes the temperature dependence of the vapor pressure.
For some compounds, like water, there are tables and formulae readily available for determining the vapor pressure at different temperatures. If you know the compound's vapor pressure at a given temperature and you also know the enthalpy of vaporization for the compound, you can then estimate the vapor pressure of the compound at another temperature. This method assumes that the enthalpy of vaporization of the compound is constant with temperature, which is only a good approximation over a relatively small temperature range. You would need to know the heat capacity of the compound to correct for the temperature dependence of the enthalpy of vaporization.
Comparison of boiling points is often used to say "compound x is more volatile than compound y" because compound x has the lower boiling point. This statement is only true for the pressure at which the boiling point was given, often 1 atmosphere. The vapor pressure of a polar compound like a low-molecular weight alcohol has a greater temperature dependence (enthalpy of vaporization) than a non-polar compound like an alkane. So an alkane and an alcohol with the same boiling point at one atmosphere will not have the same boiling point at another pressure. Correspondingly, an alkane and an alcohol with similar vapor pressures at one temperature can have very different vapor pressures (volatilities) at another temperature.