Question

Hexane and methanol are miscible as gases but only slightly soluble in each other as liquids. Explain.

Short answer

Hexane and methanol are immiscible with each other in a liquid state because methanol is a polar molecule and hexane is a non-polar molecule.

Step-by-step solution

Solubility as gases

All gases are miscible to each other. There are no intermolecular forces as such between hexane and methanol in a gaseous state. Gases would mix with each other to occupy the entire space.

Solubility as liquids

Solubility of any substance depends on the following condition: like dissolves like means polar substances can dissolve in a polar solvent and vice versa. Here, hexane is a non-polar molecule and methanol is a polar molecule having a polar –OH group. So, both these molecules cannot interact with each other because dipole interactions already present between the methanol molecules won’t allow them to mix with a non-polar molecule.

Hence methanol and hexane are immiscible as liquids because of their difference in polarity.