Conductometry:

So far we have discussed potentiometric methods. In these methods we measure the emf of a galvanic cell which is operating near zero current. Because, this emf is a function of the ionic activities within the cell, it can be used to measure ionic concentrations within titration, biological samples, water samples, and other industrial and environmental samples.  You have also looked that both potentiometry and pH metry are most widely used electroanalytical technique. In this unit you will study another electroanalytical technique called the conductometry, which is one of the oldest and in many ways simplest among the other electroanalytical techniques. This technique is based on the measurement of electrolytic conductance.

An application of electrical potential across the solution of an electrolyte involves the transfer of mass and charge from one part of the solution to the other. Such transport processes enable an insight into the structure of such solution. A transport property of great significance, that could be simply measured, is the conductance. Since an electrolytic solution consists of ions and the nature of interaction existing in the medium could be better understood in terms of the conducting power of these ions, it is more convenient to speak of conductance rather than resistance. The conducting ability of electrolytic solutions provides a direct prove of the existence of ions in solutions. The experimental determinations of the conducting properties of electrolytic solutions are very important as they can be used to study quantitatively the behaviour of ions in solutions. They could also be used to denote the values of many physical quantities such as solubilities and solubility product of sparingly soluble salts, ionic product of self ionizing solvents, hydrolysis constant of salts and dissociation constants of weak acids and bases and to form the basis for conductometric titration methods.

Objectives

After studying this unit, you will be able to:

• define electrolytic conduction,
• differentiate among the electrolytes and non-electrolytes solutions; and strong and weak electrolytes,
• explain conductance of solutions, molar and equivalent conductivities,
• describe different factors effecting conductance, and
• elaborate the method of operation of a coductometer to measurement of conductance.