Question

Choose the correct representation of conductometric titration of benzoic acid vs sodium hydroxide

• A.
• B.
• C.
• D.

Hint:

During titration of a weak acid with a strong base, the conductance increases due to the formation of a salt and further ionization of the strong base.

Answer 1

The Correct Option is C

Conductometric titration is a method used to measure the electrical conductivity of a solution as a reagent is added. In this context, we're looking at the conductometric titration of benzoic acid with sodium hydroxide.

Conductometric titration involves observing changes in conductivity as the titration progresses. For the titration of a weak acid like benzoic acid with a strong base like sodium hydroxide, the curve typically shows a decrease in conductivity followed by an increase.

1. Initial Decrease: When sodium hydroxide (a strong base) is added to the benzoic acid solution, the H⁺ ions from the benzoic acid are neutralized. This leads to the formation of water and a decrease in the concentration of hydrogen ions, which decreases the conductivity at first.
2. Neutralization Point: At the equivalence point, the amount of benzoic acid is equivalent to the amount of sodium hydroxide added. This is where the decrease in conductivity is at its minimum.
3. Post Equivalence Increase: After the equivalence point, excess hydroxide ions from added sodium hydroxide increase the conductivity, as OH^- ions contribute more to conductivity than the benzoate ions.

From the options given, the correct graph representation would depict an initial decrease followed by an increase after the equivalence point. Thus, the option with  correctly represents this behavior. 

The correct answer is (C) :

(A) → (B) Free \(H^+\) ions are replaced by \(Na^⊕\) which decreases conductance. 
(B) → (C) Un-dissociated benzoic acid reacts with \(NaOH\) and forms salt which increases ions & conductance increases. 
(C) → (D) After equivalence point at (3), \(NaOH\) added further increases \(Na^⊕\) & \(OH^⊙\) ions which further increases the conductance.

This graph logically represents the conductometric titration process for benzoic acid against sodium hydroxide, making Option 3 the correct answer.