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.

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: ΔH°f[CO2(g)] = –393.5 kJ/mol, ΔH°f[H2O(l)] = –285.8 kJ/mol, ΔH°f[H2O(g)] = –241.8 kJ/mol)

DrBob222 · Answer

C8H8 + 10 O2 ==> 8CO2 + 4H2O 42.62 kJ/gram. Convert to kJ/mole which will be delta Hrxn. Then DHrxn = (n*DHproducts)-(DHreactants) and solve for DH styrene/mol.