Question

why the compounds with high intermolecular forces have low pressure ?

Answer 1

High intermolecular forces keep molecules of the compound together. As a result, it is harder for these molecules to break out of the solids or liquids into the gas. As forces are high, the motion of the particles is reduced, and the pressure produced by the molecules is low. Low intramolecular forces result in the formation of a gas phase characterized by fast movements of the molecules that possess high pressure.