To calculate the enthalpy change for the combustion of methane gas, we first need to determine the number of moles of methane burned and then use the heat released to find the enthalpy change per mole of methane.The molar mass of methane CH4 is:C: 12.01 g/molH: 1.01 g/molCH4: 12.01 + 4 1.01 = 16.05 g/molNow, we can find the number of moles of methane burned:moles of CH4 = mass of CH4 / molar mass of CH4moles of CH4 = 34.0 g / 16.05 g/mol = 2.118 molSince we know the heat released 802 kJ and the number of moles of methane burned 2.118 mol , we can calculate the enthalpy change per mole of methane:H = heat released / moles of CH4H = -802 kJ / 2.118 mol = -378.85 kJ/molThe negative sign indicates that the reaction is exothermic, meaning heat is released during the combustion of methane. Therefore, the enthalpy change for the combustion of methane gas at standard conditions is -378.85 kJ/mol.