7) find ah° for the reaction c3hg(8) + 5 o2(8) - 3 co2(8) + 4 h2o(l). ah° = -2046 kj for the reaction: c3h8(8) + 5 o2(8) - 3 co2(g) + 4h2o(8) the heat of vaporization of water is 44.0 kj/mol. the standard enthalpy of formation of water and water vapor are -285.9kj/mol and -241.8 kj/mol, respectively. note that h20 is a liquid in the first reaction and a gas in the second. 0-1870 kj 0- kj o-2002 kj 0-2090 kj