Question

Which one of the following is incorrect for ideal solution ?

• A. $\Delta H_{mix} = 0 $
• B. $\Delta U_{mix} = 0 $
• C. $\Delta P = P_{obs} - P_{calculated \,by\, Raoult?? \,law} = 0 $
• D. $\Delta G_{mix} = 0$

Answer 1

The Correct Option is D

To determine which option is incorrect for an ideal solution, let's explore each of the given options in the context of ideal solutions in chemistry:

1. $\Delta H_{mix} = 0$: This statement is correct for an ideal solution. In an ideal solution, there is no enthalpy change upon mixing, meaning the intermolecular forces between different components are similar to those within the pure components.
2. $\Delta U_{mix} = 0$: This is also correct for an ideal solution. The internal energy change upon mixing is zero because the energy associated with intermolecular interactions does not change.
3. $\Delta P = P_{obs} - P_{calculated\,by\,Raoult's\,law} = 0$: This is true for an ideal solution. Raoult's law states that the vapor pressure of an ideal solution is directly proportional to the mole fraction of the solvent, so any deviation indicates non-ideal behavior.
4. $\Delta G_{mix} = 0$: This option is incorrect for an ideal solution. The Gibbs free energy change upon mixing is not zero; instead, it is negative, indicating a spontaneous mixing process. A zero change in Gibbs free energy would imply no tendency or driving force for mixing, which does not define the behavior of ideal solutions.

Therefore, the incorrect statement is $\Delta G_{mix} = 0$, as the process of forming an ideal solution is spontaneous and is associated with a negative Gibbs free energy change. This ensures that mixing occurs naturally without the need for external work.