What is Heat of Reaction?
In simple words, The heat of a reaction is the amount of energy needed to carry out the specified reaction; it is negative for exothermic reactions and positive for endothermic reactions. Here for an endothermic reaction, ∆H is positive whereas ∆H is negative for those reactions which produce heat.
When the given reaction is carried out at constant volume, the heat required to affect the reaction is nothing but an increase in the Internal Energy (∆U) through the ∆H/∆U will be negative for Endothermic and positive for Exothermic reaction.
Heat of Reaction Formula
The heat of reaction also known as Enthalpy of Reaction is the difference in the enthalpy value of a chemical reaction under constant pressure. It is the thermodynamic unit of measurement used to determine the total amount of energy produced or released per mole in a reaction. As a result, the heat of a chemical reaction may be defined as the heat released into the environment or absorbed while the reaction occurs at constant pressure and temperature. Joule (J) is the unit used to measure the total quantity of heat received or released.
In chemical reactions, heat is mostly transferred between the reacting system as one medium and the surrounding as the other one. Before and after the chemical transformation, the amount of heat energy is the same. In other words, the heat acquired or lost in a reacting system is equivalent to the heat gained or lost in the surroundings.