Ideal And Non Ideal Solutions

To understand which mixture forms a maximum boiling azeotrope, let's first review the concept of azeotropes:

• Azeotrope: An azeotrope is a mixture of two or more liquids that maintains a constant boiling point and composition throughout distillation. This occurs due to the specific intermolecular interactions within the mixture.
• Maximum Boiling Azeotrope: These azeotropes occur when the boiling point of the mixture is higher than that of any of its components. This results from particularly strong attractive forces between the components.

Now, let's evaluate each option:

• Water + Nitric acid: This mixture forms a maximum boiling azeotrope. When mixed, water and nitric acid create strong hydrogen bonds and dipole-dipole interactions, leading to a higher boiling point than either pure component.
• Ethanol + Water: This mixture forms a minimum boiling azeotrope, as the boiling point of the mixture is lower than either pure ethanol or water.
• Acetone + Carbon disulphide: This mixture does not form an azeotrope, and their boiling behavior does not show maximum boiling characteristics.
• Heptane + Octane: These components are non-polar hydrocarbons that do not typically form azeotropes due to a lack of significant intermolecular forces beyond van der Waals forces.

Thus, the mixture that forms a maximum boiling azeotrope is Water + Nitric acid.

This azeotropic behavior is characterized by its constant boiling point at a particular composition, where the mixture has stronger interactions compared to its individual components.

To solve this question, let's analyze the properties of an ideal solution based on the given options:

1. at constant and :
   In an ideal solution, the entropy of mixing, , is actually greater than 0. This is because the mixing process increases the randomness of the molecules, resulting in a positive change in entropy.
2. at constant and :
   For ideal solutions, the volume of mixing, , is typically zero. This means there is no change in volume upon mixing, as the intermolecular forces are similar between different components of the solution.
3. at constant and :
   This statement is true for ideal solutions. In an ideal solution, the enthalpy of mixing, , is zero because the interactions between the molecules in the mixture are similar to those in the pure components. Thus, there is no heat absorbed or evolved.
4. at constant and :
   The Gibbs free energy of mixing, , is typically negative for mixing processes, as mixing is a spontaneous process. Hence, it cannot be zero under these conditions for an ideal solution.

From this analysis, we conclude that the correct answer is: at constant and .