[VISUAL] A student obtains a mixture of the liquids hexane and octane, which are miscible in all pro — Solutions Chemistry Question

STEPS:

1. Analyze the mixture and the given data:
The student is attempting to separate a homogeneous liquid mixture of hexane ($\text{C}_6\text{H}_{14}$) and octane ($\text{C}_8\text{H}_{18}$). The physical properties provided in the table are:
* Hexane: Boiling point of $69^\circ\text{C}$; Density of $0.66\text{ g/mL}$.
* Octane: Boiling point of $126^\circ\text{C}$; Density of $0.70\text{ g/mL}$.

2. Recall the chemical principles of filtration:
Filtration is a separation technique used to separate heterogeneous mixtures (such as an insoluble solid suspended in a liquid) based on differences in particle size. Because hexane and octane are completely miscible liquids, they form a single-phase homogeneous solution where individual molecules are mixed at the molecular level, making filtration impossible.

3. Recall the chemical principles of distillation:
Distillation is an analytical technique used to separate a homogeneous mixture of miscible liquids based on differences in their boiling points (which stem from differences in the strengths of their intermolecular forces).

4. Apply distillation to the hexane-octane mixture:
* Because octane is a larger molecule than hexane, it has a larger, more polarizable electron cloud, resulting in stronger London dispersion forces and a significantly higher boiling point ($126^\circ\text{C}$ vs. $69^\circ\text{C}$).
* When the homogeneous mixture is heated, the liquid with the lower boiling point (hexane) will readily vaporize first.
* The resulting vapor, which is highly enriched in hexane, passes through a cooling condenser where it condenses back into a pure liquid and is collected in a separate vessel, leaving the higher-boiling octane behind. This matches Option D.

*

WHY_OTHERS_WRONG:

• Option A is incorrect: Filtration is designed to separate mixtures based on particle size (solid from liquid), not liquid density. Furthermore, both components are liquids in a homogeneous solution and cannot be filtered.
• Option B is incorrect: Filtration will not work because both hexane and octane molecules are extremely small and will pass through the relatively huge pores of filter paper with the exact same ease.
• Option C is incorrect: Although distillation is the correct separation technique, the separation is driven by differences in boiling points, not differences in liquid densities. Liquid density has no effect on vaporization or condensation during distillation.