Combustion Reaction

What are Combustion Reactions?

A combustion reaction is a chemical reaction which a fuel undergoes oxidation by reacting with an oxidizing agent, resulting in the release of energy (usually in the form of heat). Combustion reactions are generally highly exothermic redox reactions between an oxidant and a fuel. The product formed in a combustion reaction is usually the oxidized fuel (which is mostly liberated in the gaseous state). This is often referred to as smoke. It is not uncommon for combustion reactions to be accompanied by flames. However, it is essential to note that not all combustion reactions result in fires.

Solid fuels like coal and wood are known to initially undergo endothermal pyrolysis, resulting in the creation of gaseous fuels. The combustion of these gaseous fuels is known to provide the heat required to drive more combustion. Also, it is not uncommon for combustion to also be sufficiently hot to generate incandescent light in the form of either a flame or some flickering. The transformation of hydrogen and oxygen into water vapour, a process widely used to power rocket engines, can be seen as a simple example of combustion. Here, hydrogen is used as a fuel and oxygen is used as an oxidizing agent. This combustion reaction is known to release over 242 kilojoules of heat per mole of fuel subjected to combustion.

Examples of Combustion Reactions in our Day-to-Day Lives

Common examples of combustion reactions that are very common in the day to day lives of human beings are provided below.

  • The combustion of LPG fuel in gas stoves for the cooking of food involves a combustion reaction between the oxygen present in the atmosphere and the liquefied petroleum gas.
  • The engines of cars, bikes, and other fossil-fuel based automobiles source their power to the combustion reaction between petrol (or diesel) with oxygen.
  • The lighting of matchsticks is also based on a combustion reaction. The red phosphorus at the tip of the matchstick is heated up by striking it on a rough surface, sparking a combustion reaction between the phosphorus and the atmospheric oxygen.
  • The explosion of fireworks is also a combustion reaction. In these redox reactions, certain specific ions are incorporated into the fuel to impart a colour to the flame.

Apart from these basic combustion reactions, many other such reactions are employed in a wide range of industries. For example, the space industry is known to exploit the combustion reaction between hydrogen and oxygen for the generation of clean energy in rocket ships.

Chemical Equations of Important Combustion Reactions

Some important combustion reactions and their chemical equations are listed below.

The combustion of methanol (sometimes referred to as ‘wood alcohol’) involves a chemical reaction between methanol and oxygen. The chemical equation for this reaction is given by:

2CH3OH + 3O2 → 4H2O + 2CO2

The combustion reactions undergone by methane are also known to yield water and carbon dioxide as products. This reaction can be represented by the following chemical equation:

CH4 + 2O2 → 2H2O + CO2

The combustion of propane, which is widely employed in cooking setups like fire grills, is represented by the following chemical equation:

2C3H8 + 7O2 → 8H2O + 6CO2

Another important combustion reaction involving the oxidation of a hydrocarbon is the combustion of ethane. The chemical equation for the reaction between ethane and oxygen that yields carbon dioxide and water is provided below.

2C2H6 + 7O2 → 6H2O + 4CO2

Naphthalene also undergoes combustion in the presence of oxygen to afford carbon dioxide gas and water. The chemical equation for this reaction is given by:

12O2 + C10H8 → 4H2O + 10CO2

Frequently Asked Questions on Combustion Reactions

What is a complete combustion reaction?

Complete combustion reactions, sometimes referred to as clean combustion reactions, involve the complete oxidation of the fuel (usually a hydrocarbon). Such reactions often liberate only water and carbon dioxide as the products. A common example of a clean combustion reaction is the combustion undergone by wax candles. Wax is a hydrocarbon which undergoes clean combustion to yield only carbon dioxide and small amounts of water as the product. It can also be noted that no ash/byproducts are left behind when the entire candle is burnt out.

What are incomplete combustion reactions?

Incomplete combustion reactions (sometimes referred to as ‘dirty’ combustion reactions) are the combustion reactions that involve the formation of by-products such as ash and soot. It is not uncommon for such combustion reactions to also liberate carbon monoxide (a highly poisonous gas with the chemical formula CO) as one of the products. A common example of an incomplete combustion reaction is the burning of wood.

List some common examples of combustion reactions.

A combustion reaction is a kind of chemical reaction in which a reaction between any combustible substance and an oxidizer takes place in order to form an oxidized product. Combustion reactions are often accompanied by fires and the release of energy in the form of heat. In most combustion reactions, a hydrocarbon normally reacts with oxygen to create carbon dioxide and water.

To learn more about combustion reactions and other important types of chemical reactions such as decomposition reactions, register with BYJU’S and download the mobile application on your smartphone.

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