What is Phosphorus Pentachloride?
Phosphorus pentachloride is a greenish-yellow crystalline solid, It is decomposed by water to form hydrochloric acid and phosphoric acid with the release of heat energy. It can also be prepared by the action of dry chlorine on phosphorus trichloride. The chemical formula for phosphorus pentachloride is PCl5. In a solid state, it exists as PCl4PCl4+PCl6PCl6-.
Phosphorus pentachloride vaporizes without dissociation in an atmosphere of phosphorus trichloride or chlorine gas. The dissociation equilibrium is shifted to the left side by the presence of the product.
Structure of Phosphorus Pentachloride
The hybridization in phosphorus pentachloride is sp3d and it has a trigonal bipyramidal geometry in gaseous and liquid states. It has two axial P−Cl bonds and three equatorial P−Cl bonds.
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Properties of Phosphorus Pentachloride
Uses of Phosphorus Pentachloride (PCl5)
It is used as a chlorinating agent.
It is used for the manufacture of penicillin and cephalosporin in the pharmaceutical industry.
Used to produce acid chlorides.
Used as a catalyst in the manufacture of acetyl cellulose and also a catalyst for condensation reactions and cyclization.
Methods of Preparation of Phosphorus Pentachloride (PCl5)
P4 + 10SO2Cl2 → 4PCl5 + 10SO2
P4 + 10Cl2 → 4PCl5
PCl3 + Cl2 → PCl5
Chemical Properties of Phosphorus Pentachloride (PCl5)
Phosphorus pentachloride dissociates as: PCl5 ⇌ PCl3 + Cl2
Reaction with water: PCl5 + 4H2O → H3PO4 + 5HCl
Reaction with metal: Zn + PCl5 → ZnCl2 + PCl3
Reactions with phosphorus pentoxide: 6PCl5 + P4O10 → 10POCl3
Reactions with sulfur dioxide: SO2 + PCl5 → POCl3 + SOCl2
Harmful Effects of Phosphorus Pentachloride
Phosphorus Pentachloride is a Reactive Chemical. Direct exposure to Phosphorus Pentachloride can cause weakness, nausea, headache, dizziness, and vomiting. It may damage the liver and kidneys.
As a precaution, one must be able to identify Phosphorus Pentachloride. It’s a crystalline solid whose color can range from white to pale yellow with a pungent odor. Phosphorus Pentachloride is a manufacturing agent for other chemicals, aluminum metallurgy, and the pharmaceutical industry.
Some of the acute health hazards that can be caused by Phosphorus Pentachloride are mentioned below:
If an individual comes in contact with Phosphorus Pentachloride, one may experience severe irritation and burning of skin and eyes with possible chronic eye damage
Breathing in Phosphorus Pentachloride can lead to irritation in the nasal cavity and throat.
If inhaled deeply, it can cause intense irritation and damage to the lungs resulting in coughing and/or shortness of breath. A medical emergency can also be caused because of higher exposure to Phosphorus Pentachloride. This can lead to fluid build-up in the lungs called pulmonary oedema with severe shortness of breath.
Exposure to Phosphorus Pentachloride can cause the development of cough, phlegm in bronchitis.
FAQs on Phosphorus Pentachloride
1. Why does PCl5 have a Trigonal Bipyramidal shape whereas IF5 Is Square Pyramidal in shape?
In PCl₅ P atom is surrounded by 5 bond pairs and has no lone pairs in it, On the other hand in IF₅, the iodine atom is surrounded by 5 bond pairs and one lone pair, therefore the shape is different in both cases. Also, the hybridization in PCl5 is sp3d and in IF5 it is sp3d2.
Note: The lone pair - lone pair causes maximum repulsion than lone pair-bond pair repulsion,
And lone pair-bond pair repulsion is more than bond pair-bond pair repulsion.
2. PCl5 - is it Acidic or Basic in Nature?
Phosphorus Pentachloride PCl5 contains empty d orbitals in the valence shell. Hence it can act as Lewis acid. (According to Lewis’s concept of acid, It is the substance with an empty orbital in a valence shell so that it can accept electron pairs.
3. What Happens When PCl5 is Heated?
When Phosphorus pentachloride (PCl5) is heated, It will decompose into phosphorus trichloride(PCl3) and chlorine gas (Cl2). If placed in water, it will form phosphoric acid (H3PO4) and hydrochloric acid (HCl) with the release of heat energy.
4. What are the uses of Phosphorus Pentachloride?
Some of the common uses of Phosphorus Pentachloride in the industry are as follow:
It is used as a catalyst in the manufacturing of acetyl cellulose the plastic film on which motion pictures are printed
It is also used as a catalyst while making organic chemicals, dyestuffs, intermediates, etc.
It is a chlorinating agent which is used in organic chemistry.
