Question

Phosphorus pentachloride

• A. On hydrolysis gives an oxo acid of phosphorus which is tribasic
• B. On hydrolysis gives an oxo acid of phosphorus which is a good reducing agent
• C. Has all the five equivalent bonds
• D. Exists as an ionic solid in which cation has octahedral structure and anion has tetrahedral structure

Answer 1

The Correct Option is A

Phosphorus pentachloride (\( \text{PCl}_5 \)) exists as an ionic solid in its solid state. It dissociates into \( \text{P}^{5+} \) cations and \( \text{Cl}^- \) anions. The cation \( \text{P}^{5+} \) adopts an octahedral geometry, while the chloride anions (\( \text{Cl}^- \)) adopt a tetrahedral geometry. This is characteristic of the ionic form of \( \text{PCl}_5 \).
1. Option (B): On hydrolysis, \( \text{PCl}_5 \) gives phosphoric acid (\( \text{H}_3\text{PO}_4 \)), which is tribasic (not the oxo acid mentioned).
2. Option (C): The oxo acid formed from \( \text{PCl}_5 \) hydrolysis is phosphoric acid, which is not a good reducing agent.
3. Option (D): In phosphorus pentachloride, phosphorus forms five bonds, but they are not all equivalent due to different electronegativities of the chlorine atoms.

Thus, the correct answer is (A), where \( \text{PCl}_5 \) exists as an ionic solid with an octahedral cation and a tetrahedral anion.

Answer 2

Phosphorus pentachloride (\( \text{PCl}_5 \)) in the solid state exists as an ionic compound. The cation, \( \text{PCl}_4^+ \), has an octahedral geometry, and the anion, \( \text{Cl}^- \), adopts a tetrahedral geometry. This ionic structure explains the formation of \( \text{PCl}_5 \) in the solid state. In the liquid phase, phosphorus pentachloride exists in a covalent form with trigonal bipyramidal geometry, but in the solid state, it takes on an ionic structure.

Thus, the correct statement is that phosphorus pentachloride exists as an ionic solid in which the cation has an octahedral structure and the anion has a tetrahedral structure.