# Calculate δhrxn for the combustion of octane (c8h18) by using average bond energies.

C8H18(l)+252O2(g)→8CO2(g)+9H2O(g) Part A Part A Calculate ΔHrxn for the combustion of octane (C8H18), a
component of gasoline, by using average bond energies. H Express your answer using three significant figures.

ΔHrxn =
-5030
kJ/mol

ΔHrxn =
-5030
kJ/mol

ΔHrxn =
-5030
kJ/mol
ΔHrxn = H r x n -5030 kJ/mol Part B Part B Calculate ΔHrxn for the combustion of octane by using
enthalpies of formation from Appendix IIB in the textbook. The
standart enthalpy of formation of C8H18 is -250 kJ/mol. H Express your answer using three significant figures.

ΔHrxn =

kJ/mol

ΔHrxn =

kJ/mol

ΔHrxn =

kJ/mol
ΔHrxn = H r x n kJ/mol Part C Part C What is the percent difference between the two results? Express your answer using two significant figures.

%

%

%
% Part D Part D Which result would you expect to be more accurate?

-the value calculated from the heats of formation

-the value calculated from the average bond energies

-the value calculated from the heats of formation

-the value calculated from the average bond energies

-the value calculated from the heats of formation
-the value calculated from the heats of formation

-the value calculated from the average bond energies
-the value calculated from the average bond energies

Part A Hn C9) -(g(-39 3.st)+1(mti,e)HE2so.+6] t3! 48.oe-21て6. 387-C-250] 346+250 paite percentaitterereo -50T+.tt6-C-so 30) = 