At 300K, the density of a certain gaseous molecule at 2 bar is double to that of dinitrogen (N₂) at 4 bar. The molar mass of gaseous molecule is

PM=dRT

For unknown molecule

$2\times \mathrm{M}={\mathrm{d}}_{\mathrm{unknown}}\mathrm{RT}$

For nitrogen gas

$4\times 28={\mathrm{d}}_{\mathrm{nitrogen}}\mathrm{RT}$

But we have

${\mathrm{d}}_{\mathrm{unknown}}=2{\mathrm{d}}_{\mathrm{nitrogen}}$

Substitute these values in equation for unknown molecule gas

$2\times \mathrm{M}=2{\mathrm{d}}_{\mathrm{nitrogen}}\mathrm{RT}$

Divide both the equation then we get

$\frac{2\times \mathrm{M}}{4\times 28}=\frac{2{\mathrm{d}}_{\mathrm{nitrogen}}\mathrm{RT}}{{\mathrm{d}}_{\mathrm{nitrogen}}\mathrm{RT}}$

M=4×28

M=112g mol^-1

Hence the required option is B