A small quantity of solid lead bromide is taken in a silica crucible and two graphite electrodes are inserted. A battery consisting of two dry cells is connected to the electrodes through a switch and an ammeter.
When the crucible containing lead bromide is heated the solid lead (II) bromide melts. Now, on pressing the switch, electricity flows through the system and a red brown gas (bromine) evolves at the anode and metallic lead deposits at the cathode.
Thus, electrolysis of lead bromide using graphite electrodes produces lead metal at the cathode and bromine gas at the anode.
The chemical reactions, which take place at the surface of electrodes are called electrode processes.
According to the theory of ionization, electrolytes are present as ions in solution. These ions are directed towards the respective electrodes by the electricity supplied.
The electrolytes can be electrolyzed only in the dissolved or molten state.
Electrolysis is a process whereby a compound is decomposed into its constituent elements when an electric current passes through an electrolyte.
A simple electrolytic cell consists of a battery, an electrolyte and two electrodes.
Electrodes are conductors in the form of wires, rods or plates which pass electricity through the electrolyte during electrolysis.
Electrodes that do not take part in chemical reactions during electrolysis are known as inert electrodes. Examples are graphite (carbon) and platinum electrodes.
Electrodes that take part in chemical reactions during electrolysis are known as active electrodes. Examples are metal electrodes such as copper and silver.
The electrode which is connected to the positive terminal of a battery is called the anode while the electrode which is connected to the negative terminal of a battery is called the cathode.
Electrolytes are substances that can conduct electricity either in molten state or in aqueous solution, and undergo chemical changes.
Electrolytes can conduct electricity because the presence of free moving ions.
Examples of electrolytes are
acid solutions
alkali solutions
salt solutions
molten ionic compounds
Ionic compounds do not conduct electricity in the solid state because the ions are held in a lattice and do not move freely. However, when they are melted or dissolved in water, they can conduct electricity. This is because the ions are free to move in the molten state or aqueous solutions.
