Question

For a particular isomer of C8H18, the combustion reaction produces 5113.3 kJ of heat per mole of C8H18(g) consumed, under standard conditions.

C8H18(g) + 25/2 O2(g) ⟶ 8CO2(g)+9H2O (g) Δ𝐻rxn=−5113.3 kJ/mol

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

Answer 1

dHo formation for the isomer = (n*dHo products) - (n*dHo reactants)
Look up dHo standard in tables for CO2 and H2O. That of O2 is zero. Plug those numbers into the above equation I gave you and solve for dHo
formation. Post your work if you get stuck.