Is PCl5 Polar or Nonpolar?

Answer: PCl5 is a nonpolar molecule since the electron pull balances it out in both the horizontal and vertical axis of the molecule. In one of these there is a linear structure and in the other there is a trigonal structure which both result in no permanent dipoles. 

Although the molecule has no dipole moment, the large amount of electrons throughout the chlorines and affinity for electrons lead the molecule to form strong temporary forces, permitting a melting point of 161˚C and a boiling point of 167˚C. As a result the molecule is a solid at standard temperature and pressure. In certain related polar solvents (typically those that themselves contain a lot of chlorine molecules) the molecule is undergo ionization by either releasing or gaining chlorine atoms. The structure shown below typically holds for the liquid and gas phases of the molecule while a more "ionic-type" compound is more present in the solid form with the cation transferring a chlorine completely to the anion and thereby binding with itself. Due to the large number of chlorines, phosphorus pentachloride is typically utilized in order to add chlorines to other molecules in reaction chains. Due to the large affinity of chlorine for electrons (electronegativity: 3.16), the molecule behaves as an acid.

PCl5 Ball and Stick Model. Created with MolView.

Caution! 

Although PCl5 is sold commercially and oftentimes is contaminated with HCl in these contexts (you can theoretically tell whether this is the case by the color - yellow means that the compound has been contaminated since the substance is supposed to be colorless), phosphorus pentachloride is an incredibly dangerous substance, reacting violently with water, being corrosive to human skin and toxic when inhaled. This is mostly due to the affinity of chlorines for electrons.