Animated Solution for Chemistry - Organic Chemistry: The highest electrical conductivity from the following aqueous solutions is of

Unlocking Electrical Conductivity

When we are asked to determine which aqueous solution has the highest electrical conductivity among a set of weak acids, we are essentially being asked to find the strongest acid. But why is that? Let's embark on a journey to understand the beautiful relationship between molecular structure and macroscopic properties like conductivity.

Electrical conductivity in a solution is driven by the presence and movement of free ions. The more ions you have, the better the solution conducts electricity.

For weak acids, which do not dissociate completely in water, the concentration of ions depends entirely on their degree of ionization, denoted by $\alpha$.

Therefore, our quest to find the highest conductivity translates directly into finding the acid that ionizes the most.

The degree of ionization $\alpha$ is a direct reflection of the acid's strength, quantified by its acid dissociation constant, $K_a$. A stronger acid will push the equilibrium forward, releasing more $H^{+}$ ions into the solution.

But what makes one acid stronger than another? The secret lies in the stability of its conjugate base. When an acid donates its proton ($H^{+}$), it leaves behind a negatively charged anion. If this resulting anion is highly stable, the acid is more willing to give up its proton in the first place.

How does a molecule stabilize a negative charge? Imagine you are holding a heavy weight; it's much easier if someone helps you pull it. In chemistry, this "help" comes from electron-withdrawing groups via the Inductive Effect (-I).

Highly electronegative atoms, like halogens, pull electron density towards themselves through the sigma bonds. This pulling effect disperses the negative charge on the oxygen atom of the carboxylate group, significantly stabilizing the conjugate base.

Let's evaluate the given options based on their electron-withdrawing power:

1. Fluoroacetic acid vs. Chloroacetic acid: Fluorine is more electronegative than Chlorine. Therefore, the $-I$ effect of $-F$ is stronger than that of $-Cl$. Fluoroacetic acid is stronger than chloroacetic acid. 2. Difluoroacetic acid vs. Fluoroacetic acid: The inductive effect is additive. Two Fluorine atoms will exert a much stronger combined pull on the electron density than a single Fluorine atom.

Because difluoroacetic acid has two highly electronegative fluorine atoms, its conjugate base is the most stabilized by the $-I$ effect. Consequently, it is the strongest acid among the choices, possesses the highest degree of ionization $\alpha$, and ultimately exhibits the highest electrical conductivity.