JEE Chemistry 2023 Question with Solution

Given: conductometric titration of benzoic acid with sodium hydroxide.

Find: the correct conductance vs volume of $\text{NaOH}$ graph.

Benzoic acid is a weak acid, so initially the conductance is low because it is only slightly ionized.

As $\text{NaOH}$ is added, benzoic acid reacts to form sodium benzoate, and the salt is highly ionized. Therefore, the conductance increases.

After the equivalence point, excess $\text{NaOH}$ adds more ions, especially $\text{OH}^-$, so the conductance increases more rapidly.

Thus, the required graph is the one that shows a small initial dip and then an increase, followed by a steeper increase after the equivalence point.

The correct option is B.

Note: The solution also contains a contradictory label saying option C, but its written explanation explicitly states Option (2) and the graph behavior matches option (2).

Given: benzoic acid is titrated with strong base $\text{NaOH}$.

Find: which conductometric curve represents the process.

The relevant reaction is

1. Initially, benzoic acid is weakly dissociated, so conductance is low.
2. On adding $\text{NaOH}$, sodium benzoate is formed and the number of ions in solution increases.
3. Beyond the equivalence point, excess $\text{NaOH}$ contributes additional $\text{Na}^+$ and $\text{OH}^-$ ions, causing a sharper rise in conductance.

Therefore, the graph must rise overall and become steeper after the equivalence point. This matches option (2), so the correct option is B.