One litre of a gas at STP weighs 1.16 g. It can possible be

$1 \mathrm{L} \mathrm{of} \mathrm{gas} \mathrm{at} \mathrm{S}.\mathrm{T}.\mathrm{P}. \mathrm{weighs} 1.16 \mathrm{g}$
$\therefore 22.4 \mathrm{L} \mathrm{of} \mathrm{gas} \mathrm{at} \mathrm{S}.\mathrm{T}.\mathrm{P}. \mathrm{weighs} 22.4 \mathrm{x} 1.16$
$= 25.984 \approx 26$
This molecular weight indicates that the given compound is C₂H₂.