please tell----chemical equlibrilum

                                                 N₂O₄ (g) 2 NO₂ (g)

Initial no. of moles                      1 mole                  

At eqm                                        1 - α                   2α

α = 20% of 1 mole = 0.2

Total number of moles at eqm = 1 - α +  2α = 1 + α = 1.2

At the start, PV = nRT

1 * V = 1 * 0.082 * 300

V = 24.6

Now at  equilibrium,

P'V = nRT

P' * 24.6 = 1.2 * 0.082 * 600

P' = 2.4 atm