Question

What is Rault's law? Write any four differences between Ideal and non-ideal solutions.

Answer 1

The vapor pressure of solution containing non-volatile solute is directly proportional to themole fraction of the solvent.
Vapor pressure of solution = apor pressure of $\propto$ mole fraction of solvent.
$P=P_A\propto X_A$
$P_A=k.X_A$ ----------(i)
K=constant
for pure solvent $X_A=1$
instead of $P_A$ put $P_A^o$
Where $P_A^o$ = Vapour pressure of pure solvent
$P_A^o$ = K.1 Vapour pressure of pure solvent
$P_A^o$ = K ---------- (ii)
$P_A=P_A^0.X_A$
V.P. of solution = V.P. of pure solvent x more fraction of solvent
Difference between Ideal and Non - ideal solution

Ideal Solution	Non-ideal Solution
An ideal solution which obeys Rault's law	Solution which do not obey Rault's law
$P_A=P_A^0.X_A$ $P_B=P_B^0.X_A$	$P_A\ne P_A^0.X_A$ $P_B\ne P_B^0.X_A$
$△H_{mixing}=$ O No change in enthalpy	$△H_{mixing}\ne$ O No change in enthalpy
$△V_{mixing}=$ O No change in enthalpy	$△V_{mixing}\ne$ O No change in enthalpy