Phosphorus pentoxide (P₂O₅) is a hygroscopic powder that sublimes at __________.

Phosphorus pentoxide (P₂O₅) is one of the most important oxides of phosphorus. It is a white, crystalline, hygroscopic solid formed when phosphorus burns in excess oxygen. The compound has a strong affinity for water, which makes it an excellent dehydrating and desiccating agent.

Structurally, phosphorus pentoxide consists of a network of P₄O₁₀ molecules, each composed of four phosphorus atoms linked to ten oxygen atoms. These molecules form a cage-like structure where each phosphorus atom is bonded tetrahedrally to oxygen atoms.

One of the key physical properties of phosphorus pentoxide is that it sublimes at around 360°C. Sublimation means it changes directly from the solid phase to the gaseous phase without passing through a liquid state. This behavior indicates strong covalent bonding within the molecule and weak intermolecular forces between P₄O₁₀ units.

Because of its hygroscopic nature, P₂O₅ readily absorbs water vapor from the air, forming phosphoric acid (H₃PO₄) or other oxyacids of phosphorus depending on the amount of moisture available. The reaction with water is highly exothermic and produces significant heat.

Key reactions:
P₄O₁₀ + 6H₂O → 4H₃PO₄

This property makes phosphorus pentoxide widely used in dehydration processes, such as removing water from organic solvents, gases, or acids. It is also utilized in the manufacture of phosphoric acid, as a drying agent, and in organic synthesis where water removal is critical.

Handling P₂O₅ requires care, as its reaction with water can be violent, and it can cause severe burns.

In summary, phosphorus pentoxide sublimes at 360°C, is extremely hygroscopic, and plays a vital role as a drying and dehydrating compound in inorganic and organic chemistry