To calculate the heat generated in the complete combustion of 1 mole of methane gas CH4 , we need to consider the balanced chemical equation for the combustion reaction:CH4 g + 2 O2 g CO2 g + 2 H2O l Now, we need to find the standard enthalpy of formation for water H2O . The standard enthalpy of formation of H2O l is -285.8 kJ/mol.Next, we will use Hess's Law to calculate the heat generated H in the reaction:H = [ moles of products standard enthalpy of formation of products ] - [ moles of reactants standard enthalpy of formation of reactants ]H = [ 1 -393.5 + 2 -285.8 ] - [ 1 -74.8 + 2 0 ]Note that the standard enthalpy of formation for O2 is 0 because it is in its elemental form.H = -393.5 - 571.6 - -74.8 H = -965.1 + 74.8H = -890.3 kJ/molTherefore, the amount of heat generated in the complete combustion of 1 mole of methane gas CH4 at constant pressure is -890.3 kJ/mol. The negative sign indicates that the reaction is exothermic, meaning heat is released during the combustion process.