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NEET Chemistry Notes p-Block Elements – Allotropic forms of Sulphur

NEET Chemistry Notes p-Block Elements – Allotropic forms of Sulphur

Allotropic forms of Sulphur

Allotropic forms of Sulphur

It exists in several allotropic forms.

  • Rhombic Sulphur NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 1
    It is common crystalline form of sulphur, yellow in colour. Melting point 114.5°C and specific gravity 2.06. Its crystals are prepared by evaporating sulphur solution in CS2. It is insoluble in water but readily soluble in CS2.
  •  Monoclinic Sulphur NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 2
    It is stable above 95.6°C. Its crystals are amber yellow in colour, melting point 119°C, specific gravity 1.98. It is insoluble in CS2. It is prepared by melting rhombic sulphur in a dish followed by cooling till crust is formed.
    NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 3
    At 95.6°C both the form are stable. This temperature is called transition temperature. S8 rings in both the forms is puckered and has a crown shape.
  • Plastic Sulphur
    It is obtained by pouring boiling sulphur into cold water. It is amber brown in colour, specific gravity 1.95 and insoluble in CS2.
  • Milk of Sulphur
    It is obtained by boiling milk of lime with sulphur and decomposing the products formed with HCl. It is used in medicines.
  • Colloidal Sulphur
    It is prepared by passing H2S through a solution of an oxidising agent such as nitric acid etc.
    NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 4
    colloidal sulphur changes into ordinary form on heating.

Sulphuric Acid (H 2SO4)

Preparation

Sulphuric acid is one of the most important industrial chemicals world wide. It is manufactured by contact process which involves three steps :

Burning of sulphur ores in air to generate S02
NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 5

Properties

 Concentrated sulphuric acid is a strong dehydrating agent.
NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 6

Uses

  • In the manufacture offertilizers.
  •  Petroleum refining
  •  In the manufacture of pigments, paints and dyestuff.
  •  Detergent industry
  • Metallurgical application
  • Storage batteries
  •  As a laboratory reagent.

Structure of Oxoacids of Sulphur

Sulphur shows following oxyacids:
NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 7
NEET Chemistry Notes p-Block Elements - Allotropic forms of Sulphur 8

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