Question

Define an ideal solution and write one of its characteristics.

Answer 1

Hint: A solution which shows properties identical to the multicomponent ideal gas system is an ideal solution. A well-known example of an ideal solution is the solution of \[n\text{-Heptane and }n\text{-Hexane}\] pair.

Complete step by step answer:
The ideal solution is defined as the solution which obeys the Raoult’s law over the entire range of concentration and temperature and during its formation there is no change in its enthalpy and volume.
So, the conditions for ideal solution are:
- it obeys Raoult’s law
-enthalpy of mixing,\[\Delta {{\text{H}}_{mixing}}=0\]
- volume of mixing,\[\Delta {{\text{V}}_{mixing}}=0\]
Thus, in ideal solutions, the interactions between the solute-solute and solvent-solvent molecules are similar to the solute-solvent interactions which is possible only if the size and polarity of the solvent and solute molecules is almost the same. Also, the vapour pressure of solution is intermediate between the vapour pressure of pure components of solute and solvent.
 Few examples of ideal solution are the solutions of following pair:
\[\begin{align}
  & n\text{-Heptane and }n\text{-Hexane; Chlorobenzene and bromobenzene}\text{.} \\
 & \text{Benzene and toluene; Ethyl bromide and ethyl iodide}\text{.} \\
 & \text{Ethylene bromide and ethylene chloride; Carbon tetrachloride and silicon tetrachloride}\text{.} \\
\end{align}\]


Additional information:
The size disparity in the macromolecule solution, between the solvent molecule and the long-chain solute molecule is taken into account in the Flory-Huggins theory which involves the deduction of entropy of mixing for a macromolecule solution.


Note:The Raoult’s law states that the partial pressure of the constituent is proportional to its mole fraction in the liquid solution at all compositions. That is, \[{{\text{P}}_{\text{A}}}=\text{P}_{\text{A}}^{{}^\circ }{{\chi }_{\text{A}}}\text{ and }{{\text{P}}_{\text{B}}}=\text{P}_{\text{B}}^{{}^\circ }{{\chi }_{\text{B}}}\] where A and B are the components and \[\chi \]is the mole fraction of the component of solution.