In chemistry and thermodynamics, the enthalpy of neutralization is the change in enthalpy that occurs when one equivalent of an acid and a base undergo a neutralization reaction to form water and a salt. It is a special case of the enthalpy of reaction. It is defined as the energy released with the formation of 1 mole of water. When a reaction is carried out under standard conditions at the temperature of 298 K (25 °C) and 1 bar of pressure and one mole of water is formed, the heat released by the reaction is called the standard enthalpy of neutralization.