Pressure exerted by 1 mole of methane in a 0.25 litre container at 300K using vander Waal's equation (given a = 2.253 atml2mol−2, b = 0.0428 lit mol−1) is
(P+n2aV2)(V - nb) = nRT
(P+2.2530.25×0.25)(0.25 - 0.0428) = 0.0821 × 300
or (P + 36.048)(0.2072) = 24.63
⇒P + 36.08 = 118.87
⇒P = 82.82 atm