Oxidation-reduction reactions form the basis of many applications of .chemistry in industry and in our daily life. Some important applications are as follows:
1. Extraction of metals. By using a suitable reducing agent, metal oxides can be reduced to metals. For example, Fe20 3 is reduced to iron in the blast furnace using coke as the reducing agent.
Fe2O3 (s) + 3C(s) à 2Fe (s) + 3CO (g)
Similarly, A1p3 is reduced to aluminium by cathodic reduction in an electrolytic cell.
Other metals such as lithium, sodium, potassium, magnesium, calcium, etc., are also obtained commercially by electrolytic methods.
2. Electrochemical cells or batteries. Electrochemical cells or batteries based on redox reactions are widely used in our day-to-day life to run a number of small and big gadgets and equipments. For example, storage cells are used to supply all the electrical needs of our cars, trucks, buses, trains, aeroplanes, etc. Similarly, electrical energy needed in the space capsule is obtained by the reaction of hydrogen and oxygen in fuel cells which are electrochemical cells using oxygen and hydrogen electrodes.
3. Photosynthesis. Green plants convert carbon dioxide and water into carbohydrates in presence of sunlight. This reaction is called photosynthesis and is sensitized by chlorophyll.
During this reaction, CO2 is reduced to carbohydrates while water is oxidised to oxygen. The energy needed for the reaction is provided by sunlight.
This reaction is a source of food for plants and animals. It also maintains a constant supply of 21% of O2 by volume in the atmosphere needed for combustion of fuels and breathing of all the living creatures in the world.
4. Supply of energy. The energy required for our daily needs is obtained by oxidation of fuels. For example, oxidation of fuels such as wood, gas, kerosene, petrol, etc. produces a large amount of energy which we need for various purposes in our daily life.
Fuels (wood, petrol, kerosene, gas) + O2 à CO2 + H2O + Other products ,Energy
Human body also needs energy for proper functioning. This is obtained by the oxidation of glucose in our body to CO2 and water.
5. Production of chemicals. Many chemicals of our daily needs such as caustic soda, chlorine, fluorine, etc., are produced by electrolysis which is based on redox reactions.
6. Quantitative analysis. Redox reactions are very useful in quantitative analysis by redox titrations. These titrations involve the reactions between oxidising and reducing agents and help in estimating the amount of unknown substances in solutions.