The given graph represent the variations of Z (compressibility factor (Z) = pV/nRT ) versus p, for three real gases A,B and C. Identify the only incorrect statement

Sol. (b) is incorrect statement because at high pressure slope of the line will change from negative to positive a. For the gas A, a = 0 and its dependence on p is linear at all pressure. b. For the gas B, b = 0 and its dependence on p is linear at all pressure. c. For the gas C, which is typical real gass 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.