Final answer:
To find the dew point pressure and composition, use Raoult's law. The same approach applies for finding the bubble point pressure and composition. The ideal solution approximation is justified for similar mixtures with similar interactions.
Step-by-step explanation:
To find the dew point pressure of the mixture and the dew composition, we can use Raoult's law. Raoult's law states that the partial pressure of each component in a mixture is equal to the vapor pressure of that component multiplied by its mole fraction in the mixture. Using this law, we can calculate the partial pressures of n-hexane, n-pentane, and n-heptane based on their respective mole fractions.
To find the bubble point pressure of the mixture and the bubble composition, we can use the same approach as in part (a), but now we'll use the mole fractions in the liquid phase instead of the vapor phase.
The ideal solution approximation can be justified for this specific mixture if the interactions between the molecules in the mixture are similar to those of an ideal solution. Ideal solutions behave as if there are no interactions between the molecules of the different components. The approximation works best for mixtures of similar molecules with similar sizes, shapes, and intermolecular forces.