PCl5: Polarity, structure and properties

Phosphorous pentachloride is an inorganic chemical compound with the molecular formula of PCl5. It mainly exists as a greenish-yellow crystalline solid. It has a strong irritating odour. The gaseous neutral molecule of phosphorous pentachloride has trigonal bipyramidal geometry due to its sp3d hybridization. It is one of the significant chlorides of phosphorous and is commonly used as a chlorinating agent and a catalyst in organic chemistry.

Polarity of PCl5

PCl5 is a non-polar compound. In its structure, the P-Cl bonds are polar but they are arranged in a symmetrical molecular geometry. As a result, the dipole moment of each bond gets cancelled out with no polar character left.

Structure of PCl5

It includes one phosphorus and five chlorine atoms. The chlorine atoms are connected to the phosphorus atom via five covalent (sigma) bonds.

Preparation of PCl5

The most common process used to prepare phosphorus pentachloride is the reaction between phosphorus trichloride and dry chlorine. The reaction is given as: PCl3(l)+Cl2(g)→PCl5(g).

Properties of PCl5

The physical and chemical properties of PCl5are discussed below:

Physical Properties

• It exists as a greenish-yellow crystalline solid.

• It has a molecular weight of 208.2 g/mol.

• It has a density of 2.1g/cm3

• It has a melting point of 160.5 °C (320.9 °F; 433.6 K).

• It has a billing point of 166.8 °C (332.2 °F; 439.9 K).

• It reacts with water and is soluble in CS2, chlorocarbons, and benzene.

Chemical Properties

• It dissolves in water to form phosphoric acid and hydrochloric acid.

  PCl5+4H2O→H3PO4+5HCl

• Phosphoryl chloride and thionyl chloride are formed after a reaction between phosphorous pentachloride and sulphur dioxide.

  PCl5+SO2→SOCl2+POCl3