Combustion Reaction: The Chemistry of Burning
by Yuvi K - December 17, 2023
Combustion Reaction – chemistry of burning
What is combustion?
Combustion is a chemical reaction between a fuel and an oxidant that generates heat. Combustion reactions occur in our day-to-day lives when we burn wood or other combustible materials to produce heat. Combustion reactions also occur in the engines of vehicles so that they can move. There could be energy changes, new products formed etc when combustion takes place.
For example, the combustion of propane gas (C3H8) with oxygen (O2):
| Reactants | C3H8 + O2 |
|---|---|
| Products | CO² + H²O + Energy (gained) |
Components of combustion
A combustion reaction is a type of chemical reaction that involves the burning of a fuel in the presence of oxygen. This type of reaction is also known as a oxidation-reduction reaction, or simply an Oxidation reaction. In order for a combustion reaction to occur, the following three components must be present:
- Fuel – The material being oxidized in the reaction. This is usually a hydrocarbon such as methane, ethane or pentane. Other fuels such as alcohols or hydrogen can also be used.
- Oxygen – The oxidizing agent in the reaction. This is usually molecular oxygen (O2).
- Heat – The energy necessary to initiate and sustain the reaction. This is usually provided by an external source, such as a flame.
Types of combustion reactions
The type of reaction that occurs in a combustion reaction depends on the ratio of the reactants present. This can be classified into three different types:
- Complete Combustion – This is a reaction in which all of the fuel is fully oxidized to form carbon dioxide and water, in the presence of oxygen. The combustion of methane is an example of a complete combustion reaction.
- Incomplete Combustion – This is a reaction in which only part of the fuel is oxidized and the remainder is incompletely oxidized to form carbon monoxide and water. The combustion of propane is an example of an incomplete combustion reaction.
- Partial Combustion – This is a reaction in which only a portion of the fuel is oxidized and the remainder is converted into carbon dioxide and water. The combustion of butane is an example of a partial combustion reaction.
Chemistry of combustion
When a combustion reaction takes place, a new set of compounds is produced, along with an increase in total energy. This reaction can be represented by the following equation:
| Reactants | CaHb + xO2 |
|---|---|
| Products | yCO2 + zH2O + energy (gained) |
Where:
- CaHb – is the fuel
- x is the number of moles of oxygen required for the reaction
- y is the number of moles of carbon dioxide produced
- z is the number of moles of water produced
- energy (gained) is the energy released in the reaction
In a complete combustion reaction, the number of moles of fuel and the number of moles of oxygen will be equal, and the net reaction equation will be as follows:
| Reactants | CaHb + aO2 |
|---|---|
| Products | aCO2 + bH2O + energy (gained) |
In an incomplete combustion reaction, the number of moles of fuel and oxygen will be unequal, and the net reaction equation will be as follows:
| Reactants | CaHb + aO2 + x(=2) |
|---|---|
| Products | aCO2 + bH2O + xCO + energy (gained) |
Conclusion
In conclusion, a combustion reaction is a type of chemical reaction that involves the burning of a fuel in the presence of oxygen. The type of reaction that takes place depends on the ratio of the reactants present, and can be classified as a complete combustion, incomplete combustion or partial combustion.
The reaction can be represented by the equation CaHb + xO2 → yCO2 + zH2O + energy (gained). The reaction produces carbon dioxide, water and energy, and the number of moles of fuel and oxygen must be equal for a complete combustion reaction.
