The combustion of 1 mole of octane, C₈H₁₈(l),To produce carbon dioxide and liquid water has $\Delta$H_r = -5471 kJ.mol^-¹at 298 K.What is the change in internal energy for this reaction?

Question

Quizplus · Accepted Answer

The change in internal energy ($\Delta U$) for a reaction can be calculated using the equation $\Delta U = \Delta H - P\Delta V$, where $\Delta H$ is the change in enthalpy and $P\Delta V$ represents the work done by the system due to volume change at constant pressure. For the combustion of octane to produce CO2 and H2O, the volume change is primarily due to the difference between the moles of gaseous reactants and products. Since the question provides the enthalpy change ($\Delta H$) as -5471 kJ/mol and does not specify the volume work done but implies standard conditions (298 K), we can infer that the internal energy change ($\Delta U$) will be slightly less than the enthalpy change due to the work done by the system in expanding against atmospheric pressure. Thus, the closest value to -5471 kJ/mol, accounting for a slight decrease due to work done, is -5460 kJ/mol.

The Combustion of 1 Mole of Octane, C8H18(l),To Produce Carbon Δ\DeltaΔ

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