Question #a036b
1 Answer
Methanol has the larger vapor pressure at room temperature because it has a lower molecular weight when compared with ethanol, which implies it has weaker intermolecular forces.
Both methanol (
However, the difference comes when the weaker London dispersion forces come into play. Ethanol has a molecular weight of
This difference in molecular weight means stronger London dispersion forces in favor of the heavier molecule - ethanol - which in turn translates into a lower vapor pressure.
As a result, the molecule that exhibits weaker intermolecular forces - methanol - will have the higher vapor pressure.
Ethanol's vapor pressure at
Check out this answer on the topic of vapor pressure and intermolecular forces:
http://socratic.org/questions/how-does-vapor-pressure-related-to-intermolecular-forces
