form POCl3-in co-ordinate covalent bond. PCl3 +1/2O2 ——POCl3
The Correct Answer and Explanation is :
The reaction you have described is the formation of phosphorus oxychloride (POCl₃) from phosphorus trichloride (PCl₃) and oxygen gas (O₂):
[ \text{PCl}_3 + \frac{1}{2} \text{O}_2 \rightarrow \text{POCl}_3 ]
Step-by-step Explanation:
- Reactants:
- PCl₃ (phosphorus trichloride) consists of one phosphorus (P) atom covalently bonded to three chlorine (Cl) atoms.
- O₂ (oxygen) is a diatomic molecule composed of two oxygen atoms held together by a double bond.
- Reaction Mechanism:
- Phosphorus trichloride reacts with oxygen gas in a stoichiometric ratio of 1:½. This means that one mole of PCl₃ combines with half a mole of O₂.
- The phosphorus atom in PCl₃ has a lone pair of electrons and can form bonds with oxygen atoms. The oxygen molecule (O₂) will undergo a cleavage to provide one oxygen atom for bonding.
- Coordination and Bond Formation:
- Phosphorus in PCl₃ has an incomplete octet, meaning it has room for more bonds. This property makes it capable of accepting a lone pair of electrons from the oxygen atom during the reaction.
- The oxygen atom from O₂ will use its lone pair of electrons to form a coordinate covalent bond with the phosphorus atom.
- The resulting product, POCl₃, consists of a phosphorus atom bonded to three chlorine atoms and one oxygen atom, forming a tetrahedral structure.
- Nature of the Bond:
- The bond formed between the phosphorus and the oxygen is a coordinate covalent bond (also called a dative bond). This is because the oxygen atom donates a lone pair of electrons to phosphorus to form the bond.
- In a coordinate covalent bond, one atom provides both electrons needed to form the bond, unlike a regular covalent bond, where each atom contributes one electron.
- Final Product:
- The product of this reaction is POCl₃, where the phosphorus atom has an expanded octet (it can accommodate more than eight electrons in its valence shell, thanks to its position in the third period of the periodic table). The oxygen atom is bonded to phosphorus via a coordinate covalent bond, completing the molecular structure of POCl₃.
Summary:
In this reaction, the PCl₃ molecule reacts with oxygen to form POCl₃, and during this process, a coordinate covalent bond is formed between the phosphorus and the oxygen atom. The oxygen donates a lone pair of electrons to phosphorus, forming a dative bond and resulting in the tetrahedral molecular structure of POCl₃.