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According to the IUPAC, an exothermic reaction is "a reaction for which the overall standard enthalpy change ΔH⚬ is negative". [4] Some examples of exothermic process are fuel combustion, condensation and nuclear fission, [5] which is used in nuclear power plants to release large amounts of energy. [6]
An endothermic process may be a chemical process, such as dissolving ammonium nitrate (NH 4 NO 3) in water (H 2 O), or a physical process, such as the melting of ice cubes. [5] The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. [1]
[2] A strongly exothermic reaction will usually also be exergonic because ΔH⚬ makes a major contribution to ΔG⚬. Most of the spectacular chemical reactions that are demonstrated in classrooms are exothermic and exergonic. The opposite is an endothermic reaction, which usually takes up heat and is driven by an entropy increase in the system.
Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue. Only birds and mammals are considered truly endothermic groups of animals.
The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion or other chemical reaction. Thermal decomposition is a chemical reaction where heat is a ...
This reaction to form carbon dioxide and molybdenum is endothermic at low temperatures, becoming less so with increasing temperature. [18] ΔH° is zero at 1855 K, and the reaction becomes exothermic above that temperature. Changes in temperature can also reverse the direction tendency of a reaction. For example, the water gas shift reaction
Van 't Hoff plot for an endothermic reaction. For an endothermic reaction, heat is absorbed, making the net enthalpy change positive. Thus, according to the definition of the slope: =, When the reaction is endothermic, Δ r H > 0 (and the gas constant R > 0), so
Endothermic gas is a gas that inhibits or reverses oxidation on the surfaces it is in contact with. This gas is the product of incomplete combustion in a controlled environment. An example mixture is hydrogen gas (H 2 ), nitrogen gas (N 2 ), and carbon monoxide (CO).