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

Conductometric titrations rely on the principle that a solution's conductance depends on the number and mobility of its ions.

For instance, the titration of the strong acid HCl with the strong base NaOH involves the gradual replacement of fast-moving H₃O⁺ ions by slower Na⁺ ions, decreasing conductance until the acid is neutralized completely.

Post-neutralization, adding NaOH introduces fast-moving OH⁻ ions, increasing conductance. However, the chloride ion concentration remains the same.

A plot of conductance against the volume of base reveals the volume needed for neutralizing acid at the intersection of two straight lines.

In the titration of a mixture of HCl and a weak acid like acetic acid with NaOH, HCl, being a stronger acid, neutralizes first.

As titration continues, acetic acid forms highly ionized sodium acetate, increasing conductance. After complete neutralization, the excess base adds OH⁻ ions, further raising conductance.

The plot shows three linear segments, with points B and C representing HCl and acetic acid neutralization, respectively.