The value of Trouton's ratio ( b/Tb) for a number of substances is 21 (where, b = molal that of vaporisation of a substance at its normal boiling point, KCal/kg. mole and Tb = normal boiling point, K). The Kis-tyakowsky equation is used for calculation of Trouton's ratio of __________ liquids.

• A. polar
• B. non-polar
• C. both (a) & (b)
• D. neither (a) nor (b)