Question

Which of the following is not correct for an ideal solution?
(A) Raoult’s law is obeyed for entire concentration range and temperatures
(B) $\Delta {H_{mix}} = 0$
(C) $\Delta {V_{mix}} = 0$
(D) $\Delta {S_{mix}} = 0$

Answer 1

As we all know that an ideal solution of a component is the one in which the intermolecular interactions are of the same magnitude or we can say that it is the homogenous solution where the interaction between the molecules of solute and solvents is exactly the same as interactions between each of their own molecules.

Complete step by step solution:
As we know that an ideal solution component (solute and solvents) is the one in which the intermolecular interactions are of the same magnitude or we can say that it is the homogenous solution where the interaction between the molecules of solute and solvents is exactly the same as interactions between each of their own molecules.
We also know that these types of solution follow Raoult’s law which states that- for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction. For example- for components A, vapour pressure as ${p_A}\alpha {\chi _A}$ are directly
Solutions which follow Raoult’s law over the entire range of concentrations and temperatures are called the ideal solutions. The ideal solution most of the time has physical properties that are closely related to the properties of the pure components. These properties include that-
If the enthalpy of solution is zero, it is considered an ideal solution. $\Delta {H_{mix}} = 0$
If the volume of mixing is also zero then it is an ideal solution hence, $\Delta {V_{mix}} = 0$
But an ideal solution does not depend on the entropy of mixing because entropy increases when two components are mixed.

Therefore, the correct answer is (D).

Note: Facts to remember: vapour pressure of a solution is the pressure exerted by the vapours in equilibrium with the solution at a particular temperature. Real solutions are different from ideal solutions as they obey Raoult’s law at high temperature and low pressure conditions.