Calculate the heats of combustion for the following reactions from the standard enthalpies of formation listed in Appendix 3. (?H°f (HgO(s)) = -90.7 kJ/mol and ?H°f (FeO(s)) = -272 kJ/mol.)
(a) 2 Hg(l) + O2(g) 2 HgO(s)
(b) C2H5OH(l) + 3 O2(g) 2 CO2(g) + 3 H2O(l)