In: Chemistry
standard enthalpy change in kJ/mol
ethene C2H4 is + 52.47
hydrogen sulfide H2S is - 52.47
sulfur dioxide SO2 is - 296.84
water liquid H2O is - 285.83
carbon dioxide CO2 is - 393.51
oxygen O2 is zero
heat of combustion for- C2H4 + 3O2 ---> 2CO2 + 2H2O
Heat of combustion = 2CO2 + 2H2O - C2H4 - 3O2
heat = 2( - 393.51) + 2( - 285.83) - ( + 52.47) - 0
Heat of combustion = - 1411.15 kJ/mol
negative means exothermic (heat released)
Similarly for
heat = 2H2S + 3O2 ---> 2H2O + 2SO2
Heat of combustion = 2H2O + 2SO2 - 2H2S - 3O2
heat = 2( - 285.83) + 2( - 296.84) - 2( - 20.63) - 0
Heat of combustion = - 1124.08 kJ/mol
negative means exothermic (heat released)