To calculate the heat released during the complete combustion of methane, we need to use the balanced chemical equation for the combustion of methane and the heat of combustion H value.The balanced chemical equation for the combustion of methane is:CH4 g + 2O2 g CO2 g + 2H2O l The heat of combustion H for methane is -890 kJ/mol.First, we need to convert the mass of methane 20 grams to moles. The molar mass of methane CH4 is 12.01 g/mol C + 4 * 1.01 g/mol H = 16.05 g/mol.Moles of methane = mass / molar mass = 20 g / 16.05 g/mol = 1.246 molesNow, we can calculate the heat released:Heat released = moles of methane * heat of combustionHeat released = 1.246 moles * -890 kJ/mol = -1108.94 kJTherefore, 1108.94 kJ of heat is released during the complete combustion of 20 grams of methane.