Oxidation: An Introduction
Oxidation Reactions are the most significant chemical reactions that affect our everyday life. The most chemical reactions that we come across in our daily life, and various others which are out of our everyday experience are either oxidation or reduction reactions.
Oxidation reactions are crucial to keep our life moving. In a simple manner, an oxidation reaction can be defined as a reaction where oxygen is added to a compound and reduction is the removal of oxygen from any compound. The oxidation reaction is always coupled with a reduction reaction, that is because when one compound gets oxidised some other compound invariably gets reduced, hence these reactions are termed redox reactions.
Effects of Oxidation reaction in Everyday Life
Have you observed the effects of oxidation reactions in everyday life? Perhaps you have, but you are not aware of them as an oxidation reaction. Let me give an example of an oxidation reaction that might be very familiar-
Rusting:
We have all seen iron catching rust. Rusting is a form of corrosion of metal. Corrosion occurs due to the degradation of a metal by the action of air and moisture in the environment. It is a result of the oxidation of the metal.
Iron catches rust because it gets oxidised in presence of air and water to form hydrated iron oxide (Fe2O3.xH2O). The iron oxide forms a reddish-brown covering on the metal surface.
4Fe + 3O2 + 2xH2O —> Fe2O3.xH2O (Rust)
Similar corrosion due to the formation of metal oxide is observed on silver (black silver oxide coating) and copper (green coating).
Rusting or corrosion damages structures with metal bodies over a long time. Bodies of cars, bridges, railways, iron railings and ships catch rust. Coating the surface of the metal with paint or enamel can save them from corroding.
Another common effect of an oxidation reaction in everyday life is the rotting of food. Foods containing fats or oil become rancid if exposed to the air for a long time. This is due to slow aerial oxidation of the fatty acids present in the food, resulting in unpleasant odour and bad taste. Food items change colour and texture along with taste and smell upon exposure to the air due to atmospheric oxidation and this phenomenon is called 'rancidity'.
Combustion
Combustion is one of the most important oxidation reactions. All combustion reactions produce energy as a by-product, they are called exothermic reactions specifically due to the emission of heat energy.
As we know, our society is dependent on energy. Fuels such as kerosene, petroleum, coal, wood and charcoal all combust in presence of air, producing heat. Natural gas containing methane undergoes combustion in presence of excess oxygen to produce carbon dioxide and water.
Coals are burnt in thermal power plants to produce electricity and natural gas is used for cooking. Thus, we can see how vital role redox reactions play in our quality of life.
Thermal energy produced from the burning of fuel not only keeps our economy running, but thermal energy is what keeps us warm and alive. Our body needs thermal energy produced from breaking down food to maintain its function. Human body can be imagined as a machine which burns and oxidises all the foodstuff supplied to it and generates energy. Carbohydrates or sugar such as glucose (C6H12O6), fructose and starch are the energy source of the body. Sugars are combusted with oxygen giving out carbon dioxide and water, along with heat.
CH4 + 2O2 —> CO2 + 2H2O
C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy
Respiration supplies oxygen to the cells, where glucose is oxidised accompanied by the production of carbon dioxide and water to provide energy to the cells to perform all the essential functions necessary for the maintenance of life. Carbon dioxide produced in cells is subsequently expelled from the body through exhalation.
Although combustion has considerable utility, its harmful effect on our lives should be given proper attention. Combustion of fossil fuel produces toxic fumes containing harmful gases like sulphur dioxide, sulphur trioxide, nitrogen oxides and carbon monoxide. Fumes and smoke from car exhaust and furnaces when released into the atmosphere cause severe air pollution. It directly harms our bodies and deteriorates our health.
Key Features
The oxidation reaction is the addition of oxygen to a compound.
The reduction reaction is the removal of oxygen from a compound.
Combustion is one of the most important oxidation reactions.
Interesting Facts
Fish can soak oxygen dissolved in water using gills for respiration.
Plants absorb oxygen through stomata in their leaves.
FAQs on Oxidation Reaction in Everyday Life
1. What are some common examples of oxidation reactions we see in daily life?
Oxidation reactions are very common in our everyday lives. The four main examples are:
- Corrosion: This is the gradual deterioration of metals, with the most familiar example being the rusting of iron.
- Rancidity: This refers to the spoilage of foods containing fats and oils when they are exposed to air, leading to an unpleasant smell and taste.
- Combustion: This is the process of burning fuels like wood, petrol, or LPG, which releases energy in the form of heat and light.
- Respiration: The biological process in our cells where glucose is broken down using oxygen to produce energy for our bodies.
2. What are the main effects of oxidation in our everyday life?
Oxidation has both damaging and essential effects. On one hand, it causes unwanted processes like the corrosion of metal structures (bridges, cars) and the spoilage of food (rancidity), which result in significant economic loss and waste. On the other hand, oxidation is vital for life. Processes like combustion provide the energy needed to power our homes and industries, while cellular respiration provides the energy required for all living organisms to function.
3. How is the respiration in our bodies similar to the combustion of a fuel?
Respiration and combustion are similar because both are exothermic oxidation reactions. In both processes, a carbon-based compound (glucose in respiration, fuel in combustion) reacts with oxygen to produce carbon dioxide, water, and a significant amount of energy. The key difference is the rate of reaction; combustion is a rapid, uncontrolled process often producing a flame, while respiration is a slow, controlled, multi-step biological process that releases energy gradually within cells.
4. Why is rusting considered an oxidation reaction, and why don't all metals rust?
Rusting is considered an oxidation reaction because it involves iron atoms losing electrons when they react with oxygen and water in the atmosphere. This forms a new compound, hydrated iron(III) oxide (Fe₂O₃·xH₂O), which is the reddish-brown substance we call rust. Not all metals rust because 'rusting' specifically refers to the corrosion of iron. Other metals like aluminium also oxidise, but they form a thin, tough, and transparent layer of aluminium oxide that protects the metal underneath from further corrosion. Noble metals like gold and platinum are highly resistant to oxidation altogether.
5. What is the difference between combustion and burning?
While often used interchangeably, there is a technical difference. Combustion is any chemical process that is a rapid oxidation reaction, producing heat and light. Burning is a specific type of combustion that is vigorous enough to produce a visible flame. Therefore, all burning is a form of combustion, but not all combustion results in a flame; for example, the slow oxidation in cellular respiration is a form of combustion but does not involve burning.
6. If oxidation causes problems like corrosion and food spoilage, how can we prevent it?
We can prevent the unwanted effects of oxidation using various methods tailored to the specific problem. To prevent corrosion of metals like iron, we can:
- Apply a protective coating like paint, oil, or grease.
- Coat the iron with a more reactive metal, a process called galvanisation (using zinc).
To prevent the rancidity of food, we can:
- Add substances called antioxidants (like BHA or BHT) that slow the oxidation process.
- Store food in airtight containers or use vacuum packing to remove oxygen.
- Flush food packages with an inert gas like nitrogen.
7. What are antioxidants and how do they relate to oxidation in food?
Antioxidants are chemical compounds that inhibit or prevent oxidation. In the context of food, they are added to products containing fats and oils to prevent them from becoming rancid. They work by reacting with oxygen themselves, essentially sacrificing themselves to protect the fatty acids in the food. Common examples used as food preservatives include Butylated Hydroxyanisole (BHA) and Butylated Hydroxytoluene (BHT), which significantly extend the shelf life of food.
