Phosphorus forms two types of halides, PX3 (X = F, Cl, Br, I) and PX5 (X = F, Cl, Br).
- Phosphorus trichloride, PCl3
- Phosphorus pentachloride, PCl5
|Phosphine, PH3||Phosphorus Trichloride, PCl3||Phosphorus pentachloride, PCl5|
|Explain||Phosphine is a highly poisonous, colourless gas and has a smell of rotten fish.||This is a type of halides.|
It is a colourless oily liquid.
|It is molecular in gas and liquid phase, but in solid state exists as [PCl4]+ PCl6]– containing tetra and hexa-coordinated phosphorous species.|
|Preparation||Phosphine is prepared by the reaction of calcium phosphide with water or dilute HCl.||It is obtained by passing dry chlorine over heated white phosphorus or by the action of thionyl chloride with white phosphorus.||Phosphorus pentachloride is prepared by the reaction of white phosphorus with excess of dry chlorine or can be prepared by the action of SO2Cl2 on phosphorus.|
|Properties||It is insoluble in water and is a weaker base than ammonia. Like ammonia, it gives phosphonium compounds with acids. For example:|
PH3 is non-inflammable when pure but becomes inflammable owing to the presence of P2H4 or P4 vapours.
In water, PH3 decomposes in the presence of light to give red phosphorus and H2.
|It has a pyramidal shape, in which phosphorus is sp3 hybridised.|
It gets hydrolysed in the presence of moisture.
|In gaseous and liquid phases, its has a trigonal bipyramidal structure.PCl5 is a yellowish white powder and in moist air, it hydrolyses to POCl3 and finally gets converted to phosphoric acid.When heated, it sublimes but decomposes on stronger heating.|
Comparison between Phosphine and Ammonia
|Decomposition by electric spark||Decomposes into elements||Decomposes into elements|
|Action with chlorine||Reacts violently to form PCl5||Reacts with chlorine to form nitrogen trichloride|
|Action with halogen acids||Forms phosphonium salts||Forms ammonium salts|
|Combustibility||Burns in air to form phosphoric acid||Burns in air to form nitrogen and water.|
|Smell||Unpleasant smell of rotten fish.||Characteristic ammoniacal smell.|
|Density||Heavier than air||Lighter than air|
|Solubility||Sparingly soluble in water||Highly soluble in water|
|Nature||Highly poisonous||Non- poisonous|
|Stability||Less stable||More stable|
|Stability of salts||Less||More|
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