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881 APPENDIX 1 TABLE A-26 Enthalpy of formation, Gibbs function of formation, and absolute entropy at 25°C, 1 atm h? 8 5° Substance Formula kJ/kmol kJ/kmol kJ/kmol-K Carbon C(s) 0 0 5.74 Hydrogen H,(g) 0 0 130.68 Nitrogen N,(g) 0 0 191.61 Oxygen 0,8 0 0 205.04 Carbon monoxide CO(g) —110,530 —137,150 197.65 Carbon dioxide CO,(®) —-393,520 —394,360 213.80 Water vapor H,0(g) —241,820 —228,590 188.83 Water H,0() —285,830 —237,180 69.92 Hydrogen peroxide = H,0,(g) —136,310 —105,600 232.63 Ammonia NH,(g) —46,190 —-16,590 192.33 Methane CH,(g) —74,850 -50,790 186.16 Acetylene C,H,(g) +226,730 +209,170 200.85 Ethylene C,H,(g) +52,280 +68,120 219.83 Ethane C,Hd(g) —84,680 -32,890 229.49 Propylene C;Hq(g) +20,410 +62,720 266.94 Propane C;Hg(g) —103,850 —23,490 269.91 n-Butane CHi(g) —126,150 —-15,710 310.12 n-Octane CgH 4(8) —208,450 +16,530 466.73 n-Octane CeHis() —249,950 +6,610 360.79 n-Dodecane CoHx(8) —291,010 +50,150 622.83 Benzene CcHg(8) +82,930 +129,660 269.20 Methyl alcohol CH,OH(g) —200,670 —162,000 239.70 Methyl alcohol CH,0H()) —238,660 —166,360 126.80 Ethyl alcohol C,H,OH(g) —235,310 —168,570 282.59 Ethyl alcohol C,H,OH()) —-277,690 —174,890 160.70 Oxygen O(g) +249,190 +231,770 161.06 Hydrogen H(g) +218,000 +203,290 114.72 Nitrogen N(g) +472,650 +455,510 153.30 Hydroxyl OH(g) +39,460 +34,280 183.70 Source of Data: From JANAF, Thermochemical Tables (Midland, MI: Dow Chemical Co., 1971); Selected Values of Chemical Thermodynamic Properties, NBS Technical Note 270-3, 1968; and API Research Project 44 (Carnegie Press, 1953).