Hexane and methanol are miscible as gases but only slightly soluble in each other as liquids. Explain.
The Correct Answer and Explanation is :
Hexane (C₆H₁₄) and methanol (CH₃OH) are two organic compounds that exhibit interesting solubility behavior due to their distinct molecular structures and polarities. As gases, hexane and methanol are miscible, meaning they can mix in any proportion without separating. However, when in liquid form, their solubility in each other is limited, indicating only slight miscibility.
The key factor influencing the solubility of hexane and methanol lies in their polarity. Methanol is a polar molecule because of its hydroxyl (-OH) functional group, which allows it to form hydrogen bonds with other polar substances. This polarity leads to strong intermolecular forces, particularly hydrogen bonding, which facilitates solubility with other polar solvents like water.
In contrast, hexane is a nonpolar hydrocarbon with a long chain of carbon and hydrogen atoms, lacking functional groups that can participate in hydrogen bonding or interact strongly with polar molecules. As a result, hexane tends to interact with other nonpolar substances through London dispersion forces, which are relatively weak compared to hydrogen bonds.
When hexane and methanol are in the gas phase, the intermolecular forces are less significant due to increased kinetic energy and greater distances between molecules. This higher energy state allows hexane and methanol to mix freely without being hindered by their differing polarities. However, when they are in liquid form, the stronger hydrogen bonding in methanol makes it less likely to mix with hexane. The nonpolar hexane molecules do not interact effectively with the polar methanol molecules, leading to limited solubility.
In summary, the miscibility of hexane and methanol as gases versus their slight solubility as liquids can be attributed to the differences in their molecular polarities and the nature of intermolecular forces involved.