The reaction between hydrochloric acid HCl and sodium hydroxide NaOH is a neutralization reaction, which can be represented by the following balanced chemical equation:HCl aq + NaOH aq NaCl aq + H2O l The standard enthalpy change for this reaction, also known as the enthalpy of neutralization, is approximately -57.3 kJ/mol. This value is negative because the reaction is exothermic, meaning it releases heat to the surroundings.