To calculate the heat released or absorbed during the combustion of 50 grams of methane, we need to first determine the number of moles of methane involved. The molar mass of methane $CH_{4}4}$ is 12.01 g/mol carbon + 4 * 1.01 g/mol hydrogen = 16.05 g/mol.Now, we can find the number of moles of methane:Number of moles = mass / molar massNumber of moles = 50 g / 16.05 g/mol 3.115 molesSince the heat of combustion of methane is -890.4 kJ/mol, we can now calculate the heat released during the combustion of 3.115 moles of methane:Heat released = number of moles * heat of combustion per moleHeat released = 3.115 moles * -890.4 kJ/mol -2773.3 kJThe heat released during the complete combustion of 50 grams of methane in oxygen at a constant pressure of 1 atm is approximately -2773.3 kJ. The negative sign indicates that the reaction is exothermic, meaning heat is released.