The enthalpy of combustion of propane, graphite and dihydrogen at 298   K are: - 2220 . 0   kJ   mol - 1 , - 393 . 5   kJ   mol - 1 and - 285 . 8   kJ   mol - 1 respectively. The magnitude enthalpy of formation of propane C 3 H 8 is _____ kJmol - 1 . (Nearest integer)

Step-by-step solution

The combustion reaction can be written as follows, C 3 H 8 g + 5 O 2 → 3 CO 2 + 4 H 2 O ;   ∆ H = - 2220 . 0   kJ   mol - 1 C graphite + O 2 g → CO 2 g   ;   ∆ H = - 393 . 5   kJ   mol - 1 H 2 g + 1 2 O 2 g → H 2 O l   ;   ∆ H = - 285 . 8   kJ   mol - 1 Now, the formation reaction of propane is 3 C graphite + 4 H 2 g → C 3 H 8   g ∆ H f = 3 ∆ H C ° graphite + 4 ∆ H C ° H 2 g - ∆ H