The given graph represents the variations of compressibility factor `Z=PV//nRT` vs `P` for three real gases `A`, `B`, and `C`.

Identify the incorrect statements.

Options

A. For the gas `A, a=0` and its dependence on `P` is linear at all pressures .
B. For the gas `A, b = 0` and its dependence on `P` is linear at all pressures .
C. For the gas `C` which is a typical real gas for which neither a nor `b =0` By knowing the minima and the point of intersection with `Z =1` a and b can be calculated .
D. At high pressure the slope is positive for all real gases .

Explanation

For gas `B` value of `Z` decreases with increases of `P` According to van der Waals' equation, at high pressure when `P` is large, `V` will be small and comparison to `Vb` can t be neglected However the `(a)/(V^(2))` may be considered negligible in comparison of `P` in van der Waals' equation
`[P+(a)/(V^(2))](V-b)=nRT`
or `P(V-b) =nRT`
or `PV -Pb =nRT`
or `(PV)/(nRT) = 1+ (Pb)/(nRT) =Z (y =mx +c)`
`Z` is greater than 1 and it increased linear with pressure .