What are raoult's law?

Raoult's law

According to Raoult's law, “the vapour pressure of any solution containing a non-volatile solute in a volatile solvent is proportional to the mole fraction of the solvent in the solution.”

Raoult's law was first given by French chemist François-Marie Raoult in the year 1887. It is applicable for a solution of two volatile liquids. It claims that the vapour pressure of the solution is proportional to the mole fraction of the solvent.

Thus, Raoult’s Law formula is:

 P = P0X

  Thus,

Psolution = Χsolvent.Psolvent

Where,

• Psolution = Vapor pressure of the solution
• Χsolvent = Mole fraction of the solvent
• Psolvent = Vapor pressure of the pure solvent

Example of Raoult’s Law

Assume a solution of volatile liquids A and B in a given beaker. Since both A and B are volatile, both particles A and B are in the vapour phase. Consequently, the vapour particles of A and B thus exert partial pressure, contributing to the total pressure above the solution.

Raoult’s Law

Raoult’s Law Also states that in equilibrium,

⇒ PA = P°AxA, PB = P°BxB

Here,

• PA = Partial pressure of A
• P°A = Vapour pressure of pure A at that temperature
• xA = Mole fraction of A in the liquid phase