The enthalpy of combustion of acetylene C2H2 is C2H2(g) + 5/2O2(g) ->2CO2(g) + H2O(l) H°rxn= -1299 kJ Calculate the enthalpy of formation of acetylene, given the following enthalpies of formation H°f[CO2(g)] = -393.5 kJ/mol ,H°f[H2O(l)] = -285.8 kJ/mol