Problem: C8H18(l)+252O2(g)→8CO2(g)+9H2O(g)Part ACalculate ΔHrxn for the combustion of octane (C8H18), a component of gasoline, by using average bond energies. Express your answer using three significant figures.ΔHrxn = _____ kJ/molPart BCalculate ΔHrxn for the combustion of octane by using enthalpies of formation from Appendix IIB in the textbook. The standard enthalpy of formation of C8H18 is -250 kJ/mol.Express your answer using three significant figures.ΔHrxn = _____ kJ/molPart CWhat is the percent difference between the two results? Express your answer using two significant figures. _____ %Part DWhich result would you expect to be more accurate?a) the value calculated from the heats of formation.b) the value calculated from the average bond energies.

FREE Expert Solution

Given reaction: C8H18(l) + 25/2 O2(g) → 8 CO2(g) + 9 H2O(g)


Part A:

Lewis Structures of the reaction:

Recall:

ΔH°rxn=Hbonds broken-Hbonds formed


Average Bond Energies: found online or in textbooks

Reactants/Broken:                        Products/Formed:

• C–H = 410 kJ/mol                       • C=O = 732 kJ/mol

• C–C = 350 kJ/mol                       • O–H = 460 kJ/mol

• O=O = 498 kJ/mol

View Complete Written Solution
Problem Details

C8H18(l)+252O2(g)→8CO2(g)+9H2O(g)

Part A

Calculate ΔHrxn for the combustion of octane (C8H18), a component of gasoline, by using average bond energies. Express your answer using three significant figures.

ΔHrxn = _____ kJ/mol


Part B

Calculate ΔHrxn for the combustion of octane by using enthalpies of formation from Appendix IIB in the textbook. The standard enthalpy of formation of C8H18 is -250 kJ/mol.Express your answer using three significant figures.

ΔHrxn = _____ kJ/mol


Part C

What is the percent difference between the two results? Express your answer using two significant figures.

 _____ %


Part D

Which result would you expect to be more accurate?

a) the value calculated from the heats of formation.

b) the value calculated from the average bond energies.