The use of an electric current to cause a chemical reaction is called Electrolysis. Electrolysis is often used to break down chemical compounds into their elements. For example molecular hydrogen (H2) and molecular Oxygen (O2) is obtain from water through electrolysis. It is because of this ability to win elements from compounds that electrolysis is used in the extraction of pure metals from their ores.
Fig. 1 Diagram of an electrolyte
A device that uses a chemical reaction to produce electricity is an electrochemical cell, also known as a voltaic cell. The diagram above shows a simple electrochemical cell.
The battery provides the current which is needed for the electrolysis.
The electrical wire conducts the electricity from the battery to the electrolyte.
The points where an electric current enters and leaves the electrolyte are called electrical conductors/electrodes. They are usually made of either graphite or platinum (inert material). The electrodes are connected to either a positive or negative terminal on the battery, thereby having both positive and negative electrodes. The positive and the negative electrodes are called the anode and the cathode respectively. It is as these electrodes that the oxidation and reduction take place.
Cathode: positive ions or cations move towards it. We call it the cathode because of this, it attracts cations.
Anode: negative ions or anions move towards it. We call it the cathode because of this, it attracts anions.
Liquids that conduct electricity via movement of mobile ions are called the Electrolyte.
2 types of electrolytes
These electrolytes are completely ionised when dissolved in water or molten. Common strong electrolytes are strong acid, strong alkali and ionic salts.
HCl → H+ + Cl–
NaCl(s) → Na+(aq) + Cl–(aq)
Weak electrolytes are only partially ionised when dissolved or molten. Common weak electrolytes are weak acids, weak electrolytes and water.
CH3COOH → CH3COO– + H+
H2O → H+ + OH-
Good to know:
The unit electric current is ampere
Coulomb (symbol C) is the SI unit of electric charge; it is approximately equal to the charge of 6.24151 × 1018 protons or −6.24151 × 1018 electrons.
Conductors are any materials that allow the passage of electricity while non conductors are materials that basically resist the electric current.
We will remember from earlier notes that metals have positive ions being packed close together in a pattern structure while delocalised electrons move throughout the structure as shown above. When an electrical current is applied to the metal, these electrons will flow causing an electric current.