A gas (Molar mass = 280g/Mol) was burnt in excess O2 in a constant volume calorimeter and during combustion the temperature of the calorimeter is increased from 298 K to 298.45 K. If the heat capacity of a calorimeter is $2.5kJ{K}^{-1}$ and the enthalpy of combustion of gas is $9kJmo{l}^{-1}$ then the amount of gas burnt is ______g.