Table of Contents
Comparison between White and Red Phosphorous:
A comparison of characteristics of white and red phosphorous is given in the following table-
Physical Characteristics:
| Property | White Phosphorous | Red Phosphorous |
|---|---|---|
| Physical State | Soft, crystalline solid which can be cut with a knife. | Amorphous powder. |
| Colour | White when pure, on exposure to air, it acquires a yellowish tinge. | Reddish Violet. |
| Smell | Garlic like smell. | No smell. |
| Hardness | Soft waxy solid. | Brittle solid. |
| Density | 1.8 | 2.2 |
| Solubility | Soluble in carbon disulfide but insoluble in water. | Insoluble in water and carbon disulfide. |
| Ignition Temperature | 35°C | 260°C |
| Melting Point | 44°C | 600-615°C |
| Boiling Point | 290°C | Very high. |
| Physiological Action | Poisonous. | Non-poisonous. |
| Electrical Conductivity | Very poor. | Poor. |
| Hygroscopy | Non-hygroscopic. | Highly hygroscopic. |
| Crystalline Structure | Rhombohedral and P4 molecules. | Cubic and macromolecular structure of P4 units. |
| Exposure to air | Undergoes oxidation. | No oxidation. |
Chemical Characteristics:
| Property | White Phosphorous | Red Phosphorous |
|---|---|---|
| Stability | Unstable and gradually changes into red phosphorous. | Stable. |
| Chemical Activity | More reactive in nature. | Less reactive in nature. |
| Combustion | Burns in the air to give P2O5. | Burns at 260°C to give P2O5. |
| Action of alkalis like NaOH | Forms phosphine gas and sodium hypophosphite. | No action. |
| Action of halogens | Forms halides readily. | Forms halides on heating only. |
| Action of Sulfur | Forms phosphorous trisulfide readily. | Forms phosphorous trisulfide on heating only. |
| Reducing properties | With conc. HNO3– Reduces nitric acid to give o-Phosphoric acid. With conc. H2SO4– o-Phosphoric acid is formed. | With conc. HNO3– Reduces HNO3 to give o-Phosphoric acid. With conc. H2SO4– o-Phosphoric acid is formed. |
| Phosphorescence | Show the phenomenon of phosphorescence on exposure to air. | Do not show phosphorescence. |
| Inter conversion | Changes to red phosphorous on heating at 250°C in an inert atmosphere. | Changes to white phosphorous when its vapours at 290°C are condensed in water. |
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