Question

Why a solution of Chloroform and Acetone shows negative deviation from Raoult's law?

Answer 1

Raoult's Law: Raoult’s law states that the partial vapour pressure of a component is equal to the vapour pressure of the pure solvent multiplied by its mole fraction in the solution.

Mathematically, Raoult’s law equation is written as;

${\mathrm{P}}_{\mathrm{solution}}={\mathrm{{\rm X}}}_{\mathrm{solvent}}.{{\mathrm{P}}^0}_{\mathrm{solvent}}$

Where,

P_solution = Vapour pressure of the solution
Χ_solvent = Mole fraction of the solvent
P⁰_solvent = Vapour pressure of the pure solvent

Negative deviation from Raoult's law in Chloroform and Acetone solution:

• In the solution of chloroform and acetone, the hydrogen bond is formed with the acetone molecule by the chloroform molecule.
• Hydrogen bonding between acetone and chloroform reduces the possibility of molecules of the mixture escaping which leads to a decrease in vapour pressure.
• Therefore, the solution indicates a negative deviation from Raoult’s law.