Calculate H rxn for the combustion of octane (C 8 H 18 ), a component of gasoline,

Calculate ΔH_rxn for the combustion of octane (C₈H₁₈), a component of gasoline, by using average bond energies and then calculate it using enthalpies of formation from Appendix IIB.

What is the percent difference between your results? Which result would you expect to be more accurate?

Appendix IIB

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Substance Aluminum Al(s) Al(g) Al³+(aq) AlCl3(s) Al₂O3(s) Barium Ba(s) Ba(g) Ba²+(aq) BaCO3(s) BaCl₂(s) BaO(s) Ba(OH)₂(s) BaSO4(s) AH (kJ/mol) AG (kJ/mol) S°(J/mol. K) 0 330.0 -538.4 -704.2 -1675.7 0 180.0 -537.6 -1213.0 -855.0 -548.0 -944.7 -1473.2 0 289.4 -483 -628.8 -1582.3 0 146.0 -560.8 -1134.4 -806.7 520.3 -1362.2 28.32 164.6 -325 109.3 50.9 62.5 170.2 9.6 112.1 123.7 72.1 132.2 Substance Beryllium Be(s) BeO(s) Be (OH)2(s) Bismuth Bi(s) BiCl3(s) Bi₂O3(s) Bi₂S3(s) Boron B(s) B(g) BCI 3(g) BF3(g) B₂H6(g) AH (kJ/mol) AG (kJ/mol) S°(J/mol. K) 0 -609.4 -902.5 0 -379.1 -573.9 -143.1 0 565.0 -403.8 -1136.0 36.4 0 -580.1 -815.0 0 -315.0 -493.7 -140.6 0 521.0 -388.7 -1119.4 87.6 9.5 13.8 45.5 56.7 177.0 151.5 200.4 5.9 153.4 290.1 254.4 232.1