CBSE Class 11th Chemistry Notes for Chapter 9 Hydrogen

             UNIT 9 HYDROGEN

 

Hydrogen is the first element in the periodic table.

Its electronic configuration is 1s¹.

 

DIHYDROGEN, H₂

Occurrence: Dihydrogen is the most abundant element in the universe. It is the principal element in the solar atmosphere.

Isotopes of hydrogen: Hydrogen has three isotopes: protium, deuterium and tritium

 

PROPERTIES OF DIHYDROGEN:

1. Physical properties:

• It is a colourless, odourless, tasteless, combustible gas.
• It is lighter than air.
• It is insoluble in water.

2. Chemical properties

• Reaction with halogens: It reacts with halogens to give hydrogen halides.
• Reaction with dioxygen: It reacts with dioxygen to form water.
• Reaction with dinitrogen: It reacts with dinitrogen to form ammonia.
• Reaction with metals: It reacts with metals to yield the corresponding hydrides.
• Reaction with metal ions and metal oxides: It reduces some metal ions in aqueous solution and oxides of metals (less active than iron) into corresponding metals.
• Reaction with organic compounds: It reacts with organic compounds to give useful hydrogenated products.

 

USES OF DIHYDROGEN

• The largest single use of dihydrogen is in the synthesis of ammonia which is used in the manufacture of nitric acid and nitrogenous fertilizers.
• Dihydrogen is used in the manufacture of Vanaspati fat by the hydrogenation of polyunsaturated vegetable oils like soybean, cotton seeds, etc.
• It is used in the manufacture of bulk organic chemicals, particularly methanol.
• It is widely used for the manufacture of metal hydrides.
• It is used for the preparation of hydrogen chloride, a highly useful chemical.
• In metallurgical processes, it is used to reduce heavy metal oxides to metals.
• Atomic hydrogen and oxy-hydrogen torches find use for cutting and welding purposes.
• It is used as a rocket fuel in space research.
• It is used in fuel cells for generating electrical energy.