PP Presentation
DHorxn = S DHof (prod) - S DHof (react)
Example: Calculate the heat of combustion of ethanol, i.e., DHorxn for
C2H5OH(g) + 7/2 O2(g) ® 2 CO2(g) + 3 H2O(g)
DHorxn = { 2 DHof (CO2) + 3 DHof (H2O) }
- {7/2 DHof (O2) + DHof (C2H5OH)}
= { 2 (-393.5 kJ) + 3 (-241.8 kJ) }
- {7/2 (0 kJ) + (-235.1 kJ)}
DHorxn = -1035.5 kJ per mol of ethanol