The standard enthalpy of neutralisation ΔHneut is the enthalpy change when an acid and a base react to form 1 mole of water under standard conditions (1.0 moldm-3, 298K, 100kPa). The enthalpy of neutralisation is the sum of the enthalpy of ionisation of the acid and base and the enthalpy of the reactionH+ + OH- → H2OThe enthalpy of neutralisation is always exothermic. To determine the enthalpy of neutralisation by experiment, the acid and base are placed in a polystyrene cup. The temperature before and after the reaction are taken. The enthalpy of the reaction can be found usingq = mcΔT