Types of Non-Ideal Solution
Application of Non-Ideal Solution
Types of Azeotropes
Application of Azeotropes
It is the solution in which solute and solvent molecules
interact with one another with different forces than
the forces interaction between the similar molecules.
Non ideal solution do not obeys the Raoult’s law.
•Raoult’s law 𝑃𝐴 = 𝑃𝐴
= Partial vapour pressure of components in its pure solvent
= Partial vapour pressure of components
There are two main situations that can cause non-ideal
solutions to form
1.Non-ideal solutions can form when forces of attraction
between dissimilar molecules are weaker than between
2. Non-ideal solutions can also form when intermolecular
forces between dissimilar molecules are larger than those
between similar molecules.
Types of Non-Ideal solution
1)Non-ideal solution showing positive deviation from
2)Non-ideal solution showing positive deviation from
•Positive deviation from raoult's law occurred when
Vapour pressure of the components is greater than
what Raoult's law expected.
•The enthalpy of mixing is positive Δmix H > 0.
•The volume of mixing is expand Δmix V> 0.
1)Acetone and Benzene
2)Ethanol and Water
Acetone and Ethanol
•Negative deviation from raoult's law occurred when
Vapour pressure of the components is less than what
Raoult's law expected.
•The enthalpy of mixing is positive Δmix H < 0.
•The volume of mixing is expand Δmix V< 0.
2)Acetone and Aniline
3)Nitric acid and water
•Azeotropes are mixtures of at least two liquids that
exhibit the same concentration at the liquid phase and
•Azeotropes do not follow Raoult’s Law. It means
these mixtures are not ideal solutions and show
deviation from Raoult’s Law.
•In these mixtures, components exhibit the same mole
fraction in the liquid phase and vapour phase.
•Solute and solvent both are in a liquid state in the
•Separation of constituents of an azeotropic mixture
by fractional distillation is not possible.
Causes of Azeotrope
Azeotropes can form only when a mixture deviates from
Raoult's law, the equality of compositions in liquid phase
and vapor phases, in vapour-liquid equilibrium and
Dalton's law the equality of pressures for total pressure
being equal to the sum of the partial pressures in real
Types of Azeotropic solution
•Positive azeotrope or minimum boiling azeotrope
•Negative azeotrope or maximum boiling azeotrope
● Those azeotropic mixtures which
show large positive deviation
from Raoult’s law at specific
composition are called positive
● Ethanol – Water (89.4 % Ethanol )
at 351.4 k
Positive azeotrope or minimum boiling azeotrope
● Those azeotropic mixtures which
show large negative deviation from
Raoult's Law at specific composition
are called negative azeotropes.
● HCl - Water System (11.1% HCl ) at
Negative azeotrope or maximum boiling azeotrope
Heterogeneous azeotropes are incompletely miscible and form
two liquid phases. Positive or Negative: A positive azeotrope or
minimum-boiling azeotrope forms when the boiling point of the
mixture is lower than that of any of its constituents.
If the constituents of a mixture are completely miscible in all
proportions with each other, the type of azeotrope is called a
homogeneous azeotrope. For example, any amount of ethanol
can be mixed with any amount of water to form a homogeneous
A binary azeotrope is an azeotropic mixture containing
two constituents. A mixture of 95% ethanol and 5%
water is an example of a binary azeotrope.
Azeotropes consisting of three constituents are called
Application of azeotropic solution
•Azeotropes are used as standards in testing gas
chromatographs, detectors, and columns.
•Azeotropes are used for the separation of
constituents of zeotropic mixtures.