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Properties of solutions
The relationships for pure component are not applicable to solutions. Which needs
modification because of the change in thermodynamic properties of solution. The
pressure temperature and amount of various constituents determines an extensive state.
The pressure, temperature and composition determine intensive state of a system.
Partial Molar properties:
The properties of a solution are not additive properties, it means volume of solution is not
the sum of pure components volume. When a substance becomes a part of a solution it
looses its identity but it still contributes to the property of the solution.
The term partial molar property is used to designate the component property when it is
admixture with one or more component solution.
A mole of component i is a particular solution at specified temperature and pressure has
got a set of properties associated with it likeVP , Sietc
. These properties are partially
responsible for the properties of solution and it is known as partial molar property
It is defined as
nM
M i
ni
T , P,
n
j
j i
M i = Partial molar property of component i.
M = Any thermodynamic property of the solution
n = Total number moles in a solution
ni=Number of moles of component I in the solution
This equation defines how the solution property is distributed among the components.
Thus the partial molar properties can be treated exactly as if they represented the molar
property of component in the solution.
The above expression is applicable only for an extensive property using
We can write
x
n
n
i i M n nM i
xi
M
i i M
xi=Mole fraction of component i in the solution.