Question

Conductivity of CH\(_3\)COOH decreases on dilution. 

Hint:

Weak electrolytes like acetic acid dissociate partially, and dilution reduces the number of ions in solution, causing a decrease in conductivity.

Answer 1

The electrical conductivity of acetic acid (CH₃COOH) diminishes upon dilution because it is a weak electrolyte that ionizes incompletely in aqueous solution. This phenomenon is attributable to the characteristics of weak electrolytes.

1. Weak Electrolyte Properties:

Acetic acid functions as a weak electrolyte, signifying that its ionization in solution is not complete. The dissociation of acetic acid in water is depicted by the following reversible equilibrium: \[ \text{CH}_3\text{COOH} (aq) \rightleftharpoons \text{CH}_3\text{COO}^- (aq) + \text{H}^+ (aq) \] A minimal proportion of acetic acid molecules dissociate into ions at any given time.

2. Impact of Dilution:

Diluting acetic acid with water leads to a reduction in the concentration of its constituent ions (\( \text{CH}_3\text{COO}^- \) and \( \text{H}^+ \)). Conductivity (\( \kappa \)) is directly proportional to the ion concentration; consequently, conductivity decreases as the solution's concentration of ions is lowered through dilution.

For weak electrolytes such as acetic acid, dilution causes a shift in the ionization equilibrium towards the right, promoting further dissociation. However, despite this increased ionization, the total number of ions in the solution diminishes with dilution, resulting in a net decrease in conductivity.

3. Rationale for Reduced Conductivity:

With increased dilution, the quantity of dissociated ions decreases, thereby lowering the solution's electrical conductivity. This relationship arises because conductivity is directly contingent upon the concentration of ions present. Therefore, even if the degree of acetic acid ionization slightly increases upon dilution, the overall ion concentration is reduced, leading to a corresponding decrease in conductivity.

Summary:

In conclusion, the dilution of acetic acid results in decreased conductivity because it is a weak electrolyte that undergoes partial ionization. The reduction in ion concentration directly correlates with a decrease in the overall electrical conductivity of the solution.