Chemistry problem

Question

For a particular isomer of C8H18, the combustion reaction produces 5093.7 kJ of heat per mole of C8H18(g) consumed, under standard conditions.

C8H18(g)+25/2O2(g)⟶8CO2(g)+9H2O(g)Δ𝐻∘rxn=−5093.7 kJ/mol

What is the standard enthalpy of formation of this isomer of C8H18(g)?

Answer 1

You need the values for ΔH_f (heats of formation) of CO₂ and H₂O(g) (make sure you pick the right H₂O enthalpy) from Thermodynamic Tables at back of your textbook.

From the equation:

9ΔH_f,H2O(g) + 8ΔH_f,CO2 - ΔH_f,Oct = ΔH_rxn = -5093.7 kJ/mole of rxn.

Solve for ΔH_f,oct

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