Conductometric Titration of Strong Acid and Strong Base

Conductometric Titration of Strong Acid and Strong Base

Conductometric Titration of strong acid and strong base:

The conductance of electrolytes depends on the number of ions and their speeds. For conductometric titration experiments, a known volume of the solution to be titrated is placed in a beaker and a conductivity cell dipped into it. The conductivity cell is now connected to one end of the Wheatstone’s bridge.

Fig: Titration of Strong acid vs Strong base

Let us consider the titration of a solution of HCl by NaOH solution. The net reaction in this neutralization reaction is the production of water from H+ and OH. The neutralization reaction can be written as-

H++ (aq) + Cl (aq) + Na+ (aq) + OH (aq) → H2O (l) + Na+ (aq) + Cl (aq)

If we cancel the common terms from both sides the net ionic reaction becomes

H+ (aq) + OH (aq) → H2O (l)

In presence of the acid or base, all the water will remain practically undissociated. However, H+ ion of the acid is gradually replaced by Na+ as NaOH is added to the acid solution. Since the ionic conductance of H+ is much higher than that of Na+ there will be a decrease in the conductance as the addition of NaOH continues. This will go on until all the acid is neutralized. If more NaOH is added after the neutralization point, the conductance of the solution in the titration vessel will again increase as the ionic mobility of OH is very large. It the conductance values are graphically plotted against the corresponding volumes of NaOH added a conductometric titration curve is obtained [Figure]. The point of intersection of the two straight lines gives the endpoint of the titration. Thus acid-based titration can be carried out conductometrically.

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