When 3-methyl- I -butene is burned to CO2 and H2O, 3149.3 kJ/mol (752.7 kcaUmol) of heat is produced. How much heat is liberated when 2-methyl-l-butene is burned? Heats of formation are" 3-methyl-l-butene,-27.40kj mol-1(6.55kcal mol-1); 2 methyl - l-butene,-35.1 kj mol -1 (-8.39 kcal mol-1). The heats of combustion of carbon and hydrogen are not necessary to work this problem.