We know that PV = nRT or P = $\frac{m}{V} \times \frac{RT}{M}$ = $\frac{dRT}{M}$ ∴ d = $\frac{PM}{RT}$ or d α $\frac{P}{T}$ (R and M are constant for a given gas) or $\frac{d_1}{d_2}$ = $\frac{P_1}{P_2} \times \frac{T_2}{T_1}$ or $d_2$ = $\frac{d_1 \times P_2 \times T_1}{P_1 \times T_2}$ $d_1$ = 5.46 $\mathrm{g\,dm}^{-3}$, $P_1$ = 2 bar, $T_1$ = 273 + 27 = 300 K, $d_2$ = ?, $P_2$ = 1 bar, $T_2$ = 273 K ∴ $d_2$ = $\frac{5.46\,\mathrm{g\,dm}^{-3} \times 1\,\mathrm{bar} \times 300\,\mathrm{K}}{2\,\mathrm{bar} \times 273\,\mathrm{K}}$ = 3.0 $\mathrm{g\,dm}^{-3}$