NEET Chemistry Notes p-Block Elements – Group-15 Elements -Phosphorus

NEET Chemistry Notes p-Block Elements – Group-15 Elements -Phosphorus

Phosphorus

Phosphorus

Preparation

• Retort process
  
• Electrothermal process

Phosphorus is obtained from direct reduction of mineral phosphorite by carbon in the presence of silica.

Important Properties

Allotropy

Phosphorus exists in three allotropic forms, i.e. white or yellow, red and black  phosphorus. These forms are inter convertible

1. White phosphorus
   It is transparent, soft, poisonous, waxy solid, shows chemiluminescence and chemically more reactive.
   
2. Red phosphorus It is the stable form of phosphorus. It is odourless, non-poisonous and less reactive.
   
   It is a polymer consists of chains of P₄ tetrahedral linked together.
3.  Black phosphorus It is obtained from white phosphorus.
   White black phosphorus. It may occur in high pressure orthorhombic, rhomfiohedral and cubic form.

Uses

• Red phosphorus is used in match industry.
• Radioactive phosphorus is used in treatment of leukaemia and other blood disorders.
•  Yellow phosphorus and zinc phosphide are used as a rat poison.

Some Important Compounds of Phosphorus

• Phosphine (PH₃) 
• Phosphorus halides (PC1₃ and PC1₅)
• Oxides of phosphorus

Phosphine (PH₃)

• It is prepared by following methods
  
• It is a colourless gas with rotten fish like smell and is highly poisonous. It explodes in contact with traces of oxidising agentslike HN0₃, Cl₂ andBr₂ vapours.
• It forms phosphides when passed through the solutions of CuS0₄, AgN0₃ or HgCl₂
  

Phosphorus Halides(PCl₃ andPCl₅)

(i) Following methods are used to prepare phosphorus halides.

Oxides of Phosphorus

Phosphorus trioxide and phosphorus pentoxide are the two oxides of phosphorus. Oxides of phosphorus exist in dimeric forms.
Phosphorus trioxide, P₄O₆ is prepared from white phosphorus.

Phosphorus pentoxide, P₄O₁₀ is obtained by burning of white phosphorus in free supply of air.

Oxoacids of Phosphorus and Nitrogen

H₂N₂C₂ (hyponitrous acid); HN0₂ (nitrous acid) and HN0₃ (nitric acid) are the oxoacids of nitrogen. Out of these HNOs is the most important. HN0₃ (cone.) is strong oxidising agent, e.g.

H₃po₃ on heating, disproportionates to give orthophospheric acid and phosphine.

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