Question

Which option is inconsistent for Raoult’s law?
A.Volume of liquid solvent $+$ volume of liquid solute $=$ volume of solution
B.The change in heat of dilution for solution $= 0$
C.Solute does not undergo dissociation in solution
D.Solute undergoes dissociation in solution

Answer 1

According to Raoult’s law it is assumed that the intermolecular forces that exist between similar molecules and different molecules are equal.

Complete step by step answer:
For an ideal solution, on mixing the two solutions or solute and the solvent there is no change in the volume of the resultant solution. This means, $\Delta {V_{mix}} = 0$.
So, volume of liquid solvent $+$ volume of liquid solute $=$ volume of solution.
Since, the interaction between solute and solvent molecules (dissimilar molecules) is identical, therefore, on diluting the mixing occurs in a manner as the mixing of identical components occurs. That is, there is no change in the enthalpy of solution on dilution.
Therefore, the change in heat of dilution for solution $= 0$.
As all the molecules (solute as well as solvent) behave as identical species, therefore, upon mixing the solute does not dissociate in the solution.

Thus, option D is the answer as it is inconsistent with Raoult's law.

Note:
Raoult’s law states that the partial pressure of solution or mixture is equal to the vapour pressure of pure solvent multiplied by its mole fraction.