To calculate the enthalpy change for the combustion of one mole of methane, we first need to determine the number of moles of methane in 2.50 grams.The molar mass of methane CH4 is:C: 12.01 g/molH: 1.01 g/molMolar mass of CH4 = 12.01 + 4 1.01 = 16.05 g/molNow, we can find the number of moles of methane in 2.50 grams:moles of CH4 = mass / molar massmoles of CH4 = 2.50 g / 16.05 g/mol = 0.1558 molWe know that the combustion of 0.1558 moles of methane releases 119.1 kJ of heat. To find the enthalpy change for the combustion of one mole of methane, we can use the following equation:H = heat released / moles of CH4H = 119.1 kJ / 0.1558 mol = 764.3 kJ/molTherefore, the enthalpy change for the combustion of one mole of methane at constant pressure is -764.3 kJ/mol. The negative sign indicates that the reaction is exothermic, meaning it releases heat.