Question

What are the appropriate conditions for the formation of an ideal solution, choose the correct option.
(A) No change in enthalpy
(B) No change in volume
(C) High solubility
(D) Both A and B

Answer 1

Hint :To solve this question, we need to understand the rule that governs the ideal solutions. So, Roult’s law defines the appropriate conditions for the ideal solution. Roult’s law says that the intermolecular force of attraction of pure solute $ (A - A) $ and pure solvent $ (B - B) $ is equal to the intermolecular force of attraction of the solution $ (A - B) $ .
Also partial pressure of solute and solvent in solution will be –
 $ \begin{gathered}
  {P_A} = {P_A}^O{\chi _A}......(let's{\text{ say for solute A)}} \\
  {{\text{P}}_B}{\text{ = }}{{\text{P}}_B}^O{\chi _B}.........(let's{\text{ say for solute B)}} \\
\end{gathered} $

Complete Step By Step Answer:
Hence, if we go through each option by keeping in mind the raoult' law, we will be able to answer this question easily.
So, our first option says that there should be no change in enthalpy and according to pour roult’s law force of attraction between the solute, solvent and the solution are same, then this means that there is no change in the energy of bond in the solution. So, neither the external heat is given out neither the heat is evolved since the bonds are the same. So there is no change in enthalpy and this option A is correct.
Coming to the next option, since the strength of bonds are the same, there is no increase or decrease in the volume of the solution. Hence, this option is also correct.
In the third option – if the solution will have a high solubility, then this will decrease the bond length and hence volume will be decreased. So, option C is incorrect.
Therefore, from the above discussion we can conclude that the correct option is Option D i.e. both A and B.

Note :
Please keep in mind for the ideal solution to form, that solution should obey the Roult’s law at all concentrations and at all temperatures, only then it can be categorized as an ideal solution. Examples are benzene and toluene.