Question

which substance has a higher vapor pressure?

Answer 1

The vapor pressure of a liquid is the equilibrium pressure of a vapor above its liquid (or solid); that is, the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container.

If the intermolecular forces between molecules in the substance are:

• relatively strong, the vapor pressure will be relatively low;

• relatively weak, the vapor pressure will be relatively high.

For example, the relatively weak dipole-dipole forces and London dispersion forces between molecules results in a much higher vapor pressure. The strong hydrogen bonding interactions are responsible for the much lower vapor pressure.