The behaviour of a real gas is usually depicted by plotting compressibility factor `Z` versus `P` at a constant temperature At high temperature and high pressure `Z` is usually more than one This fact can be explained by van der Waals' equation when .

Options

A. The constant a is negligible and not b
B. The constant b is negligible and not a
C. Both the constants a and b are negligible
D. Both the constants a and b are negligible

Explanation

From van der Waals' equation,
`[P+(a)/(V^(2))][V-b]=RT..(1)`
`Z = (PV)/(nRT), if Z gt 1 then PV gtnRT`
Which is possible from (1) when `(a)/(V^(2))` is negligible
`P (V-b) =RT`
or `PV =RT +Pb`
or `PV gtRT` .