Gaseous \[{{N}_{2}}{{O}_{4}}\] dissociates into gaseous \[N{{O}_{2}}\]according to the reaction \[[{{N}_{2}}{{O}_{4}}(g)\rightleftharpoons 2N{{O}_{2}}(g)]\] At 300 K and 1 atm pressure, the degree of dissociation of \[{{N}_{2}}{{O}_{4}}\] is 0.2. If one mole of \[{{N}_{2}}{{O}_{4}}\] gas is contained in a vessel, then the density of the equilibrium mixture is:

• A. 1.56 g/L          
• B. 6.22 g/L
• C. 3.11g/L            
• D. 4.56 g/L