Conductometric Titrations: Strong Acid-Weak Base and Weak Acid-Strong Base Titrations

Consider the titration of a weak acid, acetic acid, against a strong base, NaOH. Initially, the conductance of acetic acid is low due to its weak dissociation.

As NaOH is added, the highly ionized sodium acetate is produced, increasing the conductance.

Once all the acid is neutralized, any additional base introduces fast-moving OH⁻ ions, leading to a sharp increase in conductance.

The plot of conductance against the volume of the base shows two intersecting lines, with the intersection point indicating the endpoint.

Contrarily, when a strong acid, HCl, is titrated against a weak base, NH₄OH, the conductance initially decreases due to the replacement of fast-moving H₃O⁺ ions by the slower-moving NH₄⁺ ions of the base.

The conductance decreases until the completion of acid neutralization, after which there is no significant change in conductance attributed to the weak dissociation of the base.

The endpoint of the titration is determined by identifying the intersection point of two lines on the conductance plot.