Gaseous $N_2O_4$ dissociates into gaseous $NO_2$ according to the reaction $N_2O_4 (g) \leftrightharpoons 2NO_2 (g)$ At $300\; K$ and $1\; atm \;pressure$, the degree of dissociation of $N_2O_4$ is $0.2$. If one mole of $N_2O_4$ gas is contained in a vessel, then the density of the equilibrium mixture is :

Question

( A ) $3.11\; g/L$
( B ) $6.22\; g/L$
( C ) $4.56\; g/L$
( D ) $1.56\; g/L$