Question

Calculate the Van der Waals constant for carbon dioxide it its critical temperature `T_(cr) = 304 K` and critical pressure `p_(cr) = 73 atm`.

Answer 1

`P_(Cr)/(RT_(Cr)) = (a//27 b^2)/(8a//27 b) = (1)/(8 b)`
Thus `b = R (T_(Cr))/(8 p_(Cr)) = (0.082 xx 304)/(73.8) = 0.043 litre//mol`
and `((RT_(Cr))^2)/(P_(Cr)) = (64 a)/(27)` or `a = (27)/(64)(RT_(Cr))^2//P_(Cr) = 3.59 (atm.litre^2)/((mol)^2)`.