Why do chloroform and benzene exhibit negative deviation from Raoult's law?
This is because when these liquids are mixed, H-bonding type interactions are formed between hydrogen atom of chloroform (partial positive charge due to 3 Cl atoms) and 'pi' electron cloud of benzene ring.﻿
Thus, chloroform-benzene interactions are stronger than chloroform-chloroform and benzene-benzene interactions.