Importance of Raoult’s law
Let’s say a volatile liquid A is placed inside a closed container. After some time, vapour particles will start to develop as a result of evaporation. The liquid particles on the surface will eventually be in dynamic equilibrium with the vapour particles of A as time goes on. As a result, the pressure that A’s vapour particles are exerting at any given temperature is known as A’s vapour pressure at that temperature. All solids and liquids display vapour pressure, which is solely dependent on the kind of liquid and temperature.
The A particles will now fill the spaces between the B particles on the surface of the solution if liquid B is introduced to this container.
A portion of the molecules on the surface of any given liquid have enough energy to convert to the vapour phase.
Since there are currently fewer A particles on the surface, there will be fewer A vapour particles in the vapour phase. This will cause A’s vapour pressure to decrease.
If B is also volatile, there will be fewer B particles in the vapour phase than there would be if B were a pure liquid.
This new pressure, which is determined by Raoult’s equation and depends on the component concentration of each liquid phase, is the partial pressure of each A and B
PA ∝ XA = XAP°A
PB ∝ XB = XBP°B
P° represents the component of the mole fraction.
Vapour Pressure
Vapour pressure is the force exerted by a liquid’s (or solid’s) vapour above the surface of the liquid. At a particular temperature and thermodynamic equilibrium, this pressure is formed in a closed container. The rate of liquid evaporation is controlled by the equilibrium vapour pressure. The vapour pressure increases with increasing temperature. When atmospheric pressure and vapour pressure are equal, a liquid is said to have reached its boiling point.