Chapter 2: ElectrochemistryClass 12 Chemistry — summary, notes, extra questions & MCQ quiz

Summary

Electrochemistry studies the relationship between chemical energy and electrical energy. In a galvanic (voltaic) cell a spontaneous redox reaction produces electricity; oxidation occurs at the anode and reduction at the cathode. Each electrode has a standard electrode potential, measured against the standard hydrogen electrode (assigned zero), and the standard cell potential is \(E^{\circ}_{cell}=E^{\circ}_{cathode}-E^{\circ}_{anode}\). The Nernst equation gives the potential under non-standard conditions, \(E=E^{\circ}-\dfrac{RT}{nF}\ln Q\), and at equilibrium relates to the equilibrium constant and to free energy through \(\Delta G^{\circ}=-nFE^{\circ}_{cell}\). Ionic conduction is described by conductivity and molar conductivity \(\Lambda_m\), which increases on dilution; for strong electrolytes it follows Debye-Huckel-Onsager behaviour and Kohlrausch's law of independent migration of ions lets us find limiting molar conductivities. Electrolysis uses electrical energy to drive non-spontaneous reactions, with the amounts deposited governed by Faraday's laws. Practical cells include the dry cell, mercury cell, lead storage battery, nickel-cadmium cell and fuel cells, while corrosion of iron is an electrochemical process that can be prevented by coating or sacrificial protection.

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