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

Answer

9

Explanation

Energy released at constant volume due to combustion of 3.5 gm of a gas `=2.5 xx 0.45`
Hence, energy released due to the combustion of 28 gm (i.e. 1 mole) of a gas `=2.5 xx 0.45 xx 28/3.5 = 9 kJ"mol"^(-1)`.