Question

In case of association, abnormal molar mass of solute will:

• A. decrease
• B. increase
• C. remain same
• D. first increase and then decrease

Hint:

In case of association, the abnormal molar mass tends to decrease due to the aggregation of solute molecules.

Answer 1

The Correct Option is B

To address the problem, it is necessary to comprehend the alteration in a solute's molar mass when association takes place within a solution.

1. Comprehending Association in Solutions:
Association describes the phenomenon where solute molecules or ions unite to form larger structures or groups, primarily driven by intermolecular forces such as hydrogen bonding. This typically transpires in polar solvents, like water, where substances such as acids, bases, or other solutes tend to aggregate into dimers, trimers, and so forth.

2. Impact on Molar Mass:
When association occurs, the observed molar mass of the solute will appear to be higher than its actual molar mass. This is attributed to the fact that association results in a reduced number of particles in the solution (fewer dissociated entities), consequently leading to colligative properties (e.g., freezing point depression or boiling point elevation) that are less pronounced than anticipated for the initial number of particles. This discrepancy consequently leads to a calculated molar mass that is elevated.

3. Core Principle:
Abnormal molar mass denotes a measured molar mass that exceeds the expected value due to the process of association. For instance, upon the formation of a dimer, the apparent molar mass will be twice the actual molar mass of the solute.

Concluding Statement:
In instances of association, the abnormal molar mass of the solute experiences an increase.