Question

How does structure affect enthalpy of fusion? Namely with p-diclhorobenzene and naphthalene

Answer 1

The factory which affects the enthalpy of fussion are

1.Molecular mass of the chemical compound increase the molecular mass increase in heat of fussion

2.it depend on structure and packing of molecules in its lattice when there is symmetry in the molecule it easily fit in crystal and form high packing and high enthalpy of fussion

3.dipole moment or polarity when polarity generate there is increase in electrostatic force and increase in heat of fussion

In case of paradicloro benzene naphthalene both have equal symmetry elements but naphthalene can fit more compacted than diclorobenzene so it should has more heat of fission on structural basis data are given as

Paradiclorobenzene 18.19 in/mol at326.2 K and naphthalene has 18.81 at 353.4K