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Write main differences between the properties of white phosphorus and red phosphorus.

Answer
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Hint: There exist many allotropic forms of phosphorus in nature. Red phosphorus and white phosphorus are two the most common and important allotropes of phosphorus. Red phosphorus is thermally more stable than white phosphorus.

Complete answer:
Main points of difference between the properties red phosphorous and white phosphorous are tabulated below:

PropertyWhite phosphorousRed phosphorous
Physical state and colourIt is a white waxy solid. It is soft and can be cut using a knife. It turns yellow in colour in exposure to light, hence, it is also called as yellow phosphorus.It is red coloured hard crystalline solid. It is lustrous in nature.
Odour It has garlic like odour.It is odourless.
Physiological propertiesIt is poisonous in nature and prolonged working this phosphorus leads to a disease known as Phossy jaw.It is non-poisonous in nature.
Structure White phosphorus exists in P4 tetrahedral structure. Each P-atom is sp3 hybridized and bonded to other three P-atoms by covalent bonds.
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Red phosphorus exists in polymeric form. Each P4 tetrahedral is linked to another to form a polymer through covalent bonds. Its melting point is higher than that of white phosphorus,
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SolubilityIt is insoluble in water but dissolves in organic solvents for example, ether, carbon disulphide, alcohols, etcIt is not soluble in water as well as organic solvents
Action of airIt shows phosphorescence. Due to high angle strain, it is very reactive. It burns in air. The greenish glow is visible in the dark It does not glow in the dark. Due to its polymeric, it is less reactive than white phosphorus. On reaction with oxygen it gives P4O10.
Reaction with halogens It spontaneously burns in chlorine to form phosphorus trichloride and phosphorus pentachloride. P4+6Cl24PCl3 P4+10Cl24PCl5 Being less reactive, it reacts with halogens only when heated. It forms PCl3 followed by PCl5. P4+6Cl2Δ4PCl3 P4+10Cl2Δ4PCl5
Reaction with sulphurIt reacts with sulphur with violently to form a number of sulphides, i.e. P2S3, P2O5, P4S3, P4S7and P4S10. P4S3 being the most stable. 8P4+3S88P4S3 It reacts with sulphur only when heated in an inert atmosphere to form sulphides. 8P4+3S8453K8P4S3
Reaction with metals It reacts with metals to convert them into phosphides. It generally does not react with metals. It may show reactions with alkali metal like Na at high temperature.
Reaction with baseWhite phosphorous when heated with solution of sodium hydroxide (NaOH) solution in inert atmosphere forms phosphine (PH3) and sodium hypophosphite (NaH2PO2). P4+3NaOH+3H2OΔ,CO2PH3+3NaH2PO2 It does show reaction with sodium hydroxide. This property is exploited to separate red phosphorus from white phosphorus.


Note: The main point to note here is that red phosphorus exists in polymeric form and thus, is less reactive than white phosphorus. White phosphorus being less stable than red phosphorus, can be converted to red phosphorus by heating at 573K for several hours.