If Z is a compressibility factor, Van der Waals equation at low pressure can be written as: (WB JEE 2014) (a) a Z =1- VRT (b) Pb Z =1- RT (c) Pb Z =1+ RT (d) RT Z =1+ Pb

The Van der Waals equation can be written as- 2 2 ( / )( ) P n a V V nb nRT For, n=1 2 ( / )( ) P a V V b RT At very low pressure, V b Therefore, 2 2 ( / )( ) P a V V RT / 1 / PV RT a VRT Also, / PV RT z (z is the compressibility factor) 1 / z a VRT