Question

Styrene, C8H8, is one of the substances used in the production of synthetic rubber. When styrene burns in oxygen to form carbon dioxide and liquid water under standard-state conditions at 25°C, 42.62 kJ are released per gram of styrene. Find the standard enthalpy of formation of styrene at 25°C.
(Given: [CO2(g)] = −393.5 kJ/mol, [H2O(l)] = −285.8 kJ/mol, [H2O(g)] = −241.8 kJ/mol)

Answer 1

C8H8 + 10 O2(g) ==> 8CO2(g) + 4H2O(l)

delta Hrxn = (8*deltaHf CO2 + 4*deltaHf H2O) - (1*deltaHfC8H8)
You can look up CO2 and H2O in tables. deltaHf for oxygen will be zero since that is its standard state and at 25 C.I would convert delta H rxn from kJ/g to kJ/mol since all of the numbers you look up for CO2 and water are in kJ/mol. The answer for delta Hf for styrene will be in kJ/mol.

Answer 2

Thank you so much!!!!