Using van der Waals equation, calculate the constant ′a′ when 2 moles of a gas confined in a 4 liter flask exerts a pressure of 11.0 atm at a temperature of 300K. The value of ′b′ is 0.05 litre mol−1
van der Waals equation for n moles of gas is:
[P + n2aV2 ] [V - nb] = nRT
Given V = 4 litre, P = 11.0 atm, T = 300K
b = 0.05 litre mol−1, n = 2
So,
[11 + 22a42 ] [4−2×0.05]=nRT
= 2×0.082×300
a = 6.46 atm litre2mol−2