The correct order of melting point of dichlorobenzenes is

Step-by-step solution

Out of the three isomers of dichlorobenzene, the para-isomer is more symmetrical than the other two isomers, So, it has a more closely packed arrangement of molecules in its crystal lattice. So, para-dichlorobenzene has a higher melting point as compared to ortho and meta Isomers. Melting point of ortho-dichlorobenzene, meta-dichlorobenzene and para-dichlorobenzene are 256K, 249K, 323K respectively. Bromo, iodo and polychloro derivatives of hydrocarbons are heavier than water. The density increases with increase in