Ideal solutions and Non- ideal solutions
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Addition of anon-volatile solute to a solvent to give a solution results in the exertion of the vapour pressure of the solution uniquely from the solvent.
o This vapour pressure is lower than the vapour pressure of the pure solvent at a given temperature.
o The surface of the solution is occupied by both solute and solvent molecules which results in the reduction of the surface for the solvent molecules. As a result the apparent number of solvent molecules escaping from the surface is reduced. This in turn reduces the vapour pressure.
o The reduction of vapour pressure of solvent depends on the quantity of non-volatile solute present in the solution not on its nature.
Ideal solutions and Non- ideal solutions
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The solutions that obey Raoult’ s law over the whole collection of concentration are known as ideal solutions. o
o
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The enthalpy of mixing of the pure components for the formation of the solution is zero. Mathematically, Δmix H = 0.
This implies that heat is neither absorbed nor evolved during the mixing of components in a solution.
The volume of mixing of the pure components for the formation of the solution is also zero. Mathematically, Δmix V = 0