where, Z= compressibility factor, p= pressure V= volume, n= number of moles R= gas constant, T= temperature, Also, curves for (Z vs p) (i) If Z>1 the gas show positive deviation from ideal behaviour and is less compressible. (ii) If Z<1, gas show negative deviation. (iii) No, real gas give a straight line parallel to (p). i.e. path way (2) and (3) only.