When the temperature of the environment is 15.4°C, the enthalpy of combustion for octane (C8H18) is –44.427 MJ/kg. The molar enthalpy of combustion for octane in these conditions is ________ kJ/mol

Answer 1

1 MJ = 10⁶ J and 1 kJ = 10³ J, so 1 MJ = 1000 kJ

The molar mass of octane (C₈H₁₈) is 114.23 g/mol,

so 1 kg octane = 1000/114.23 = 8.754 mol octane

1 MJ/kg = (1000 kJ)/( 8.754 mol) = 114.23 kJ/mol

–44.427 MJ/kg = (114.23)(–44.427) kJ/mol = –5075.9 kJ/mol

Answer

–5075.9