[AirForceOne]

Ok I'm getting all confused about identifying the interparticle forces of molecules.

a) PCl3
My answer: Dipole-Dipole
Correct answer: Dipole-Dipole, LDF
b) CO2
My answer: LDF
Correct answer: LDF
c) Cl2
My answer: LDF
Correct answer: LDF
d) ICl
My answer: Dipole-Dipole
Correct answer: Dipole-Dipole, LDF
e) KCl
My answer: Ionic bonding
Correct answer: Ionic bonding

According to my teacher's notes, LDF "To all molecules"? Then how come letter e doesn't have LDF also? When is a molecule LDF or not LDF? I'm all confused.

This correct problems and answers get me confused even more about LDF...
CH3F - dipole-dipole
CH4 - LDF
HF - Hydrogen bonding, LDF
HCl - Dipole-Dipole, LDF
GeH4 - LDF

Thanks.

[Bakegaku]

Any molecule, especially a weakly polar or nonpolar one can be affected by random distribution of electrons causing forces between molecules.  In the case of an ionic molecule like KCl, though, it's not an interaction between molecules of KCl and KCl.  Essentially the entire lattice could be considered a macromolecule, where each K⁺ is bonded to 6 Cl^- ions and visa versa.  KCl is only the emperical formula.  Since ionic forces are all that are keeping the lattice together, the London Dispersion Force is ommited from this answer.