Fugacity: It is derived from Latin, expressed as fleetness or escaping ...

Modifying equation (a)
RT
V
dP
1
d ln i
i
RT
i - Represents fugacity of the component i in the solution.
Ideal solutions
An ideal mixture is one, which there is no change in volume due to mixing. In other
words for an ideal gaseous mixture partial molar volume of each component will be equal
to its pure component volume at same temperature and pressure.
i i V V and Vi xi
xiVi
P
V --- Raoults law
Ideal solutins are formed when similar components or adjacent groups of group are
mixed i i V V
Eg: Benzene-Toluene
Methanol- Ethanol
Hexane- Heptane
Solutin undergo change in volume due to mixing are known as non ideal solutions
i i V V
Eg: Methanol-Water
Ethanol-water.
Ideal solutions formed when the intermolecular force between like molecules and unlike
molecules are of the same magnitude.
Non-ideal solutions are formed when intermolecular forces between like molecules and
unlike molecules of different magnitude.
For ideal solutions
t
V niVi
-------------------(1)
Vi is the molar volume of pure component I
t V
Vi T
, P , n j Vi
----------------- (2)
ni
The residual volume for the pure component is
RT
Vi
p
Therefore we know from reduced properties
P
f i 1 RT
ln Vi
dP ----(3)
P RT P
0
For component i in terms of partial molar properties