Question

The heat of combustion of liquid octane (C ₈H ₁₈ ) to carbon dioxide and liquid water at 298 K is -1303 kJ/mol. What is the standard enthalpy change (ΔH∘) for this reaction?

a) -1303 kJ/mol
b) 1303 kJ/mol
c) 651.5 kJ/mol
d) -651.5 kJ/mol

Answer 1

The standard enthalpy change for the combustion of liquid octane to carbon dioxide and liquid water at 298 K is -1303 kJ/mol, indicating an exothermic reaction.

Step-by-step explanation:

The standard enthalpy change (ΔH°) for the combustion of liquid octane (C₈H₁₈) to carbon dioxide and liquid water at 298 K is -1303 kJ/mol. This value represents the amount of heat released when one mole of octane combusts in oxygen under standard conditions to form carbon dioxide and water. It is important to note that the enthalpy change is given as a negative number because the reaction is exothermic, meaning that it releases heat.