What is Vapor Pressure?

What is vapor pressure? I got this question last week from my Junior labmate. Since I work in vapor pressure term every day, I have to learn it well. Below are my note in vapor pressure.

Vapor pressure (also known as equilibrium vapor pressure), is the pressure of a vapor in equilibrium with its non-vapor phases. All liquids and solids have a tendency to evaporate to a gaseous form, and all gases have a tendency to condense back into their original form (either liquid or solid). At any given temperature, for a particular substance, there is a pressure at which the gas of that substance is in dynamic equilibrium with its liquid or solid forms. This is the vapor pressure of that substance at that temperature. The equilibrium vapor pressure is an indication of a liquid’s evaporation rate. It relates to the tendency of molecules  and atoms to escape from a liquid or a solid. A substance with a high vapor pressure at normal temperatures is often referred to as volatile.


Fig. 1 Ilustration of Vapor Pressure

Factors that affect vapor pressure are as follows : Continue reading

By Ianatul Khoiroh Posted in Thermo