Be sure to answer all parts.
Calculate the heats of combustion for the following reactions. Use the standard enthalpies of formation.
(a) C2H4(g) + 3O2(g) -> 2CO2(g) + 2H2(l)
(b) 2H2S(g) + 3O2(g) -> 2H2O(l) + 2SO2(g)
_____kJ/mol