The balanced chemical equation for the reaction between hydrogen gas and oxygen gas to produce water is:2 H g + O g 2 HO l The given enthalpy change of -483.6 kJ/mol is for the formation of 2 moles of water from 2 moles of hydrogen gas and 1 mole of oxygen gas. Since the reaction is already balanced and the enthalpy change is given for the specified amounts of reactants, the enthalpy change for the reaction between 2 moles of hydrogen gas and 1 mole of oxygen gas to produce water is -483.6 kJ.