11.2 litre of a gas at STP weighs 14g. The gases could be

11.2L of an ideal gas at STP =0.5 moles.0.5 moles 14g ​= 1 mole 28g​It could be any gas that have molar mass equal to  28g/mole. (Nitrogen, molar mass=28g/mol)⟹ The gas could be N2​,CO,C2H4.