To calculate the standard enthalpy change H for the reaction of methane CH and oxygen O to form carbon dioxide CO and water vapor HO , we need to use the following equation:H = Hf products - Hf reactants where Hf is the standard enthalpy of formation for each compound.The balanced chemical equation for the reaction is:CH g + 2 O g CO g + 2 HO g Now, we need the standard enthalpies of formation Hf for each compound:Hf CH = -74.8 kJ/molHf O = 0 kJ/mol since O is in its elemental form Hf CO = -393.5 kJ/molHf HO = -241.8 kJ/mol for water vapor Now, we can plug these values into the equation:H = [1 -393.5 + 2 -241.8 ] - [1 -74.8 + 2 0]H = -393.5 - 483.6 - -74.8 H = -877.1 + 74.8H = -802.3 kJ/molSo, the standard enthalpy change for the reaction of methane gas and oxygen gas to form carbon dioxide gas and water vapor is -802.3 kJ/mol.