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 solid-state, it exists as [PCl₄]⁺ [PCl₆]⁻ .
Phosphorus pentachloride vaporizes without dissociation in an atmosphere phosphorus trichloride or chlorine gas. The dissociation equilibrium is shifted to the left side by the presence of the product.
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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Formula of phosphorus pentachloride
phosphorus pentachloride shape
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.
P₄ + 10SO₂Cl₂ → 4PCl₅ + 10SO₂
P₄ + 10Cl₂ → 4PCl₅
PCl₃ + Cl₂ → 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
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.
Question: Why PCl₅ Has Trigonal Bipyramidal Shape Whereas IF₅ Is the Square Pyramidal in Shape?
Answer: 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.
Question: PCl₅ - is it Acidic or Basic in Nature?
Answer: Phosphorus Pentachloride PCl₅ contain 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.
Question: What Happens When PCl₅ is Heated?
Answer: 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.
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