A 79.9-L sample of a gaseous hydrocarbon, measured at 1.00 atm pressure and 25.0°C,

is burned in excess oxygen, liberating 4.24 × 10^3 kJ of heat at constant pressure. What
is the identity of the hydrocarbon? (R = 0.0821 L · atm/(K · mol))
Substance H°f (kJ/mol)
CO2(g) –393.5
H2O(l) –285.8
A) ethane (C2H6, H°f = –84.68 kJ/mol)
B)B) ethylene (C2H4, H°f = 52.47 kJ/mol)
C) propane (C3H8, H°f = –104.7 kJ/mol)
D) acetylene (C2H2, H°f = 226.73 kJ/mol)
E) propylene (C3H6, H°f = 20.41 kJ/mol)