enthalpy of reaction

chemical reaction

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June 26, 2026

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The enthalpy of reaction, represented by (\Delta H), is the heat added or removed during a chemical reaction to maintain a constant temperature. If the pressure remains constant, this heat change is equivalent to the change in enthalpy, which is the difference between the enthalpy of the products and reactants.12

A reaction is endothermic if (\Delta H) is positive, meaning heat is absorbed. Conversely, a reaction is exothermic if (\Delta H) is negative, indicating heat is released. Breaking chemical bonds requires energy, while forming them releases energy. The net energy change determines whether a reaction is endothermic or exothermic.13

Hess's law states that the total enthalpy change for a chemical reaction is constant, regardless of the steps involved. This principle allows for the calculation of reaction enthalpies using known data, such as heats of formation.41

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heat of reaction
…pressure is also designated the enthalpy of reaction, represented by the symbol ΔH. If the heat of reaction is positive, the reaction is said to be endothermic; if negative, exothermic.
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…pressure is also designated the enthalpy of reaction, represented by the symbol ΔH. If the heat of reaction is positive, the reaction is said to be endothermic; if negative, exothermic.
Read More