To calculate the enthalpy change H for the combustion of methane gas, we need to use the following equation:H = q_p = mcTwhere:q_p = heat absorbed or released at constant pressurem = mass of the substance in this case, methane c = specific heat capacity of the substanceT = change in temperatureFirst, we need to find the moles of methane CH4 using its molar mass:Molar mass of CH4 = 12.01 g/mol C + 4 * 1.01 g/mol H = 16.05 g/molNow, we can find the moles of CH4:moles of CH4 = mass / molar mass = 5.5 g / 16.05 g/mol = 0.3427 molNext, we need to find the heat of combustion of methane H_combustion . The standard heat of combustion of methane is -890.4 kJ/mol. Since the combustion is exothermic, the heat is released, and the value is negative.Now, we can find the heat released q_p during the combustion of 0.3427 mol of CH4:q_p = moles of CH4 * H_combustion = 0.3427 mol * -890.4 kJ/mol = -305.1 kJNow, we can use the equation H = mcT to find the specific heat capacity c of methane:c = H / m * T = -305.1 kJ / 5.5 g * 14.6C = -3.8 J/gCFinally, we can calculate the enthalpy change H for the combustion of 5.5 grams of methane gas:H = mcT = 5.5 g * -3.8 J/gC * 14.6C = -305.1 kJSo, the enthalpy change H for the combustion of 5.5 grams of methane gas at constant pressure 1 atm is -305.1 kJ.