Chemistry · Ch 9 — Electrochemistry
Introduction
Introduction
Every material you've ever handled falls into one of three electrical categories: conductor, semiconductor or insulator. Copper and aluminium carry electricity across the country's power grid; the plastic sheathing around the wire keeps that same electricity from going anywhere it shouldn't. This unit is about a fourth, less obvious category -- electrolyte solutions -- and the chemistry of how they conduct, and how that conduction can be harnessed to do useful electrical work.
What this unit sets out to do. By the end of it you should be able to:
- recognise the conductivity of an electrolytic solution, and define resistivity, conductivity, equivalent conductivity and molar conductivity;
- explain how conductivity varies with concentration;
- apply Kohlrausch's law to calculate the conductivity of a weak electrolyte at infinite dilution;
- describe an electrochemical cell, and differentiate an electrochemical cell from an electrolytic cell;
- represent a galvanic cell using IUPAC cell notation;
- derive the Nernst equation and apply it to calculate ;
- define Faraday's laws of electrolysis;
- describe how batteries are constructed;
- explain corrosion as an electrochemical process.
Walther Nernst, who this unit's Nernst equation is named after, won the 1920 Nobel Prize in Chemistry for the Nernst heat theorem, which helped establish the third law of thermodynamics. His 1887 equation -- originally derived for the electrical potential across a membrane separating unequal ion concentrations -- is now central to both electrochemistry and cell physiology.