Question:
In conductometric titration of acetic acid with 0.1 N sodium hydroxide, complete neutralization occurs. Further addition of titrant results in
In conductometric titration of acetic acid with 0.1 N sodium hydroxide, complete neutralization occurs. Further addition of titrant results in
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In weak acid–strong base conductometric titrations, conductance increases sharply after the equivalence point due to the presence of excess hydroxide ions.
Updated On: Jul 14, 2026
- Increase the conductance
- Decrease the conductance
- No change in the conductance
- Colour change (orange to red)
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The Correct Option is A
Approach Solution - 1
Conductometric titration involves the measurement of electrical conductance during a chemical reaction. When titrating a weak acid like acetic acid (CH\textsubscript{3}COOH) with a strong base like sodium hydroxide (NaOH), the neutralization reaction is:
\[
\text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O}
\]
Initially, conductance is low due to partial ionization of acetic acid. As NaOH is added, H\textsuperscript{+} ions are replaced by highly mobile Na\textsuperscript{+} ions, slightly increasing conductance. At the equivalence point, the solution contains sodium acetate, which is a salt of a weak acid and contributes moderately to conductance.
Beyond the equivalence point, excess NaOH adds OH\textsuperscript{−} ions, which are very mobile and significantly increase the conductance. Thus, further addition of titrant (NaOH) after neutralization leads to a noticeable increase in conductance.
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Approach Solution -2
The question asks what happens to conductance when NaOH is added beyond the point where it has fully neutralized acetic acid in a conductometric titration.
- Increase the conductance: Once all the acetic acid has reacted, any further NaOH added stays unreacted in solution as free Na+ and OH- ions. Hydroxide ions have very high ionic mobility, among the highest of any common ion in water, so adding more of them steadily pushes the conductance upward.
- Decrease the conductance: A decrease would only make sense if ions were being consumed or replaced by less mobile ones, which is not happening here. Past neutralization, ions are simply being added, not removed, so a decrease does not fit.
- No change in the conductance: If conductance stayed flat, it would mean the added ions were not contributing to conduction at all, which contradicts the fact that OH- is highly mobile and freely dissociated once in excess.
- Colour change (orange to red): This describes what happens with a visual indicator, not what a conductance measurement shows. Conductometric titration is followed by measuring conductance directly, without needing a colour-changing indicator at all.
Since post-neutralization NaOH simply adds highly mobile hydroxide ions to the solution without removing anything, the measured conductance rises steadily beyond the neutralization point.
Therefore, the correct answer is Increase the conductance.
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