Are combustion reactions always exothermic and type of reaction which has two compounds in the reactants and two compounds in the products?
Dear Prof. Rk Naresh
- Please you can check the textbook "Statistical Thermodynamics: An Engineering Approach" (2019) by Prof. John W. Daily. Cambridge University Press.
Chapters 6, 11 and 14.
Kind Regards.
Yes, combustion reactions are always exothermic, meaning they release heat energy to the surroundings. However, not all reactions with two compounds in the reactants and two compounds in the products are combustion reactions. Combustion reactions are a specific subset of exothermic reactions where a substance reacts with oxygen, typically producing carbon dioxide and water as products.
The double bond in O2 is much weaker than other double bonds or pairs of single bonds, and therefore the formation of the stronger bonds in CO2 and H2O results in the release of energy, which is given off as heat or increases thermal motion. This explains why fire is hot regardless of fuel composition. Combustion is a high-temperature exothermic redox (oxygen adding) chemical reaction between a fuel and an oxidant, usually atmospheric oxygen that produces oxidized, often gaseous products, in a mixture termed as smoke. All combustion reactions are always exothermic which occur in the presence of excess air or oxygen. Substances acting as fuels undergo combustion when heated. It is not necessary that a particular substance undergoing combustion may burn also. Chemical reactions that release energy are called exothermic. In exothermic reactions, more energy is released when the bonds are formed in the products than is used to break the bonds in the reactants. Chemical reactions that absorb (or use) energy are called endothermic. Combustion reactions are almost always exothermic. As when wood burns, it must do so in the presence of O2 and a lot of heat is produced: Wood as well as many common items that combust are organic. Double displacement reactions are those in which two compounds in a solution reacts to form two new compounds by mutual exchange of radicals. This type of reaction is also known as double decomposition reaction. A double displacement reaction, also known as a double replacement reaction or metathesis, is a type of chemical reaction where two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products. A combustion reaction can be defined as a reaction in which a substance burns in oxygen with the release of carbon dioxide, water, and energy in the form of heat, light, and even sound. It is always exothermic.
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