In a constant volume calorimeter, $3.5 \mathrm{~g}$ of a gas with molecular weight $=28$ was burnt in excess oxygen at $298.0 \mathrm{~K}$. The temperature of the calorimeter was found to increases from $298.0 \mathrm{~K}$ to $298.45 \mathrm{~K}$ due to the combustion process. Given, that the heat capacity of the calorimeter is $2.5$ $\mathrm{kJ} \mathrm{K}^{-1}$, the numerical value for the enthalpy of combustion of the gas in $\mathrm{kJ} \mathrm{mol}^{-1}$ is