1 Relative
Lowering of
Vapour
Pressure
Rationalised 2023-24
16
Chemistry
The expression on the left hand side of the equation as mentioned
earlier is called relative lowering of vapour pressure and is equal to
the mole fraction of the solute The above equation can be written as:
10
01
1
p – p  
p
 = 
2
1
2
 
 

n
n
n
 
2
2
1
2
since 







n
x
n
n
(1 26)
Here n1 and n2 are the number of moles of solvent and solute
respectively present in the solution For dilute solutions n2 < < n1,
hence neglecting n2 in the denominator we have
10
1
0
1
p
p
p

= 
2
1
n
n
(1