Ideal solutions and Non- ideal solutions
o
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
o
The solutions that obey Raoult ’ s law over the whole collection of concentration are known as ideal solutions . o
o
o
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