Electrolysis - The basics
- Electrolysis involves splitting up a substance using electricity.
- Ionic substances can be electrolysed when they are molten or in solution.
- In electrolysis positive ions (cations) move to the negative electrode (the cathode) and negative ions (anions) move to the positive electrode (the anode).
Changes at the electrodes
- In electrolysis, the ions move towardes the oppositely charged electrodes.
- At the electrodes, negative ions are oxidised while positve ions are reduced.
- Reactions where reduction and oxidation happen are called REDOX reactions (REDuction and OXidation).
- When electrolysis happens in water, the less reactive element is usually produced at an electrode.
- When we electrolyse brine we get three products - Chlorine gas, hydrogen gas and sodium hydroxide solution.
- Chlorine is used to kill microbes in drinking water and swimming pools, and to make hydrochloric acid, disinfectants, bleach and plastics.
- Hydrogen is used to make margarine and hydrochloric acid.
- Sodium hydroxide is used to make bleach, paper and soap.
*Diagram of electrolysising brine on the first revision card!*
- Copper extracted from its ore contains impurities such as gold and silver.
- Copper is purified by electrolysis to remove these impurities.