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
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
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.
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.
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
Properties
Concentrated sulphuric acid is a strong dehydrating agent.
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: