In a constant-volume calorimeter, 3.5g of gas with molecular weight 28 was burnt in excess oxygen at 298.0K. The temperature of the calorimeter was found to increase from 298.0K to 298.45K due to the combustion process. Given that the heat capacity of the calorimeter is 2.5kJK−1 , the numerical value for the enthalpy of combustion of the gas in kJmol−1 is