Question

Indicate which of the following molecular characteristics will be expected to increase the solubility of a simple solute in an aqueous solution:

• A. A high melting point
• B. The presence of polar group
• C. A high molecular surface area
• D. A high boiling point

Answer 1

The Correct Option is B

To determine which molecular characteristic will likely increase the solubility of a simple solute in an aqueous solution, we need to consider the interaction between the solute molecules and water molecules, which are polar.

1. Presence of a polar group: The presence of polar groups in a molecule greatly enhances its solubility in water. Polar molecules can form hydrogen bonds or dipole-dipole interactions with water, facilitating dissolution. For example, molecules with hydroxyl (-OH) or amino (-NH₂) groups are typically more soluble in water due to their polarity.
2. High melting point: A high melting point often indicates strong intermolecular forces within the solid structure. While this could imply a solid structure without empty spaces for water, it does not directly correlate with solubility in water. Thus, a high melting point does not inherently enhance solubility.
3. High molecular surface area: Larger molecules with greater surface areas tend to have more extensive dispersion forces. This can hinder their solubility in water because nonpolar regions do not interact favorably with water. Hence, a large surface area is unfavorable for solubility if the surface is nonpolar.
4. High boiling point: Similar to a high melting point, a high boiling point reflects strong intermolecular forces within a liquid. While this might cause the molecule to have strong internal cohesion, it is not necessarily an indicator of increased solubility in water.

Therefore, the correct option is The presence of polar group. Polar groups promote solubility by allowing better interaction with water molecules through hydrogen bonding or dipole-dipole attractions.