Learning Objectives Aft er learning this unit, the students will be able to  Recognise the conductivity of

electrolylic solution  Defi ne the terms resistivity, conductivity

equivalent and molar conductivity  Explain the variation of conductivity

with concentration  Apply Kohlrausch law to calculate the

conductivity of weak electrolyte at infinite dilution.

 Describe an electrochemical cell  Diff erentiate between an

electrochemical and electolylic cell  Represent a galvanic cell using IUPAC

cell notation  Derive Nernst equation and apply it to

calculate Ecell.  Defi ne Faraday’s Law of electrolysis  Describe the construction of batteries  Explain corrosion as an electrochemical

process.

ELECTRO CHEMISTRY

UNIT

9

Walther Hermann Nernst

Walther Hermann Nernst, was a German chemist known for his work in thermodynamics, physical chemistry, electrochemistry, and solid state physics. His formulation of the Nernst heat theorem helped to pave the way for the third law of thermodynamics, for which he won the 1920 Nobel Prize in Chemistry. He is also known for developing the Nernst equation in 1887. He also derived the Nernst equation for the electrical potential generated by unequal concentrations of an ion separated by a membrane that is permeable to the ion. His equation is widely used in cell physiology and neurobiology.

INTRODUCTION We have come across many materials in our life, and they can be broadly classified

into conductors, semiconductors and insulators based on their electrical conductivity. You might have noticed that conducting materials such as copper, aluminium etc., are used to transport electrical energy from one place to another place, and the insulating materials such as PVC, Bakelite etc., in switches, circuit boards etc., Do you know how the electrical energy is generated? We know from first Law of thermodynamics that energy can neither be created nor be destroyed, but one form of energy can be converted into another form. It is not possible to create electrical energy but we can generate electrical energy in many ways i.e., by converting solar energy, wind energy, tidal energy etc…. one such a way is converting chemical energy into electrical energy as in the case of batteries. We cannot imagine a modern technological world without batteries. Hence it is important to know the principles behind this type of energy conversion. The branch of chemistry that deals with the study of electrical energy transport and the inter conversion of electrical and chemical energy is called electrochemistry. Electrochemical reactions are redox reactions and they involve the transfer of electron from one substance to another.

In this unit, we will learn about the electrical conduction, construction of batteries and the thermodynamic principles involved in electro chemical reactions.