Fuels And Combustion

The relationship between the enthalpy ( ) and internal energy ( ) can be given by the following equation: Where: - is the change in enthalpy (given as -2546 kJ/mol), - is the change in the number of moles of gas in the reaction,
- is the gas constant ( ),
- is the temperature in Kelvin (298 K at 25°C). In the case of combustion, the combustion products (carbon dioxide and water) usually result in no change in the number of moles of gas ( ).
Therefore, the internal energy change is equal to the enthalpy change : Hence, the internal energy change for the reaction is -2544.8 kJ/mol.