A gas (Molar mass $=280 \mathrm{~g} \mathrm{~mol}^{-1}$ ) was burnt in excess $\mathrm{O}_2$ in a constant volume calorimeter and during combustion the temperature of calorimeter increased from 298.0 K to 298.45 K . If the heat capacity of calorimeter is $2.5 \mathrm{~kJ} \mathrm{~K}^{-1}$ and enthalpy of combustion of gas is 9 kJ mol" ${ }^1$ then amount of gas burnt is $\_\_\_\_$ g. (Nearest Integer)