Electrochemistry: Introduction

Unit ‒ III

Electrochemistry

INTRODUCTION

Electrochemistry is a branch of chemistry, which deals with the chemical applications of electricity. Electrochemistry deals with the chemical reactions produced by passing electric current through an electrolyte or the production of electric current through chemical reactions. 

1. Conductors

A substance or material that allows electric current to pass through it is called a conductor. The ability of a material to conduct electric current is called conductance.

Examples: All metals, graphite, fused salts, aqueous solutions of acids, bases, etc., 

2. Non‒Conductors or Insulators

Materials which do not conduct electric current are called non‒conductors or insulators.

Examples: Plastics, wood, most of the non metals, etc., 

Types of Conductors

The conductors are broadly classified into two types as follows.

1. Metallic conductors or Electronic conductors

Metallic conductors are solid substances, which conduct electric current due to the movement of electrons from one end to another end. The conduction decreases

with increase of temperature.

Examples: All metals, graphite.

2. Electrolytic Conductors

Electrolytic conductors conduct electric current due to the movement of ions in solution or in fused state. The conduction increases with increase of temperature.

Examples: Acids, bases, electrovalent substances.

Types of Electrolytic Conductors

The electrolytic conductors are further sub-classified into three types as follows:

(a) Strong electrolytes

Strong electrolytes are substances, which ionize completely almost at all dilutions.

Examples: HCl, NaOH, NaCl, KCl, etc.,

(b) Weak electrolytes

Weak electrolytes are substances, which ionise to a small extent even at high dilutions.

Examples: CH₃COOH, NH₄OH, CaCO₃, etc.,

(c) Non electrolytes

Non electrolytes are substances, which do not ionise at any dilutions.

Examples: Glucose, sugar, alcohol, petrol, etc.,

Table 3.1 Differences between metallic conduction and electrolytic conduction

Cell Terminology

(i) Current

Current is the flow of electrons through a wire or any conductor. Unit is ampere

(ii) Electrode

Electrode is a material (or) a metallic rod/bar/strip which conducts electricity.

(iii) Anode

Anode is the electrode at which oxidation occurs.

(iv) Cathode

Cathode is the electrode at which reduction occurs.

(v) Electrolyte

Electrolyte is a water soluble substance forming ions in solution, and conducts an electric current.

(vi) Anode Compartment

Anode compartment is the compartment of the cell in which oxidation half‒reaction occurs. It contains the anode.

(vii) Cathode Compartment

Cathode compartment is the compartment of the cell in which reduction half reaction occurs. It contains the cathode.

(viii) Half‒cell

Half cell is a part of a cell, containing electrode dipped in an electrolytic solution. If oxidation occurs at the electrode that is called oxidation half cell. If reduction occurs at the electrode that is called reduction half cell.

(ix) Cell

Cell is a device consisting two half cell. The two half cells are connected through one wire.