Notes On Dihydrogen: Preparation - CBSE Class 11 Chemistry
Hydrogen is the third most abundant element on the earth. It constitute 15.4% earth's crust and ocean Isotopes:  Hydrogen has 3- isotopes, they are, 1.Protium (1H1) 2.Deuterium (1H2) 3.Tritium (1H3) The position of hydrogen in the periodic table is debated because it has similar properties like Alkali metals and Halogen. The hydrogen is placed with Alkali metals. The modern periodic table is based on electronic configuration the electronic configuration of Hydrogen is 1s  hence it is placed in First group. Preparation of Dihydrogen: Laboratory preparation of Dihydrogen: 1)  In laboratory it is prepared by the reaction of granulated zinc with dil.Hcl. Zn + 2HCl → ZnCl2 +H2 ↑ 2) Other laboratory method is by the action of metals like Zn, Al on strong alkalis like NaOH or KOH Ex: Zn + 2NaOH → Na2ZnO2 + H2↑ Commercial preparation of Hydrogen:  Hydrogen is prepared by the electrolysis water using Platinum electrode. Here sulphuric acid is used to acidify water. When electric current is passed through water it decomposes to hydrogen and oxygen. Hydrogen gas is released at cathode and oxygen gas is released at anode.         2H2O $\underset{\to }{\text{Electricity}}$  2H2 + O2 Mechanism: H2O ↔ H++OH- At anode: OH- - e- →OH OH+ OH→ H2O + O O + O → O2 ↑ At cathode: H+ + e- → H H + H → H2 ↑ Industrially Hydrogen is prepared by  passing steam over red hot coke or hydrocarbons at high temperature in the presence of Nickel catalyst. The products are CO and Hydrogen.   CH4 + H2O $\underset{\to }{\text{Ni}}$ CO + 3 H2 Water gas:  The mixture of  carbon monoxide and Hydrogen is called water gas(CO + H2)   Water gas is used in the preparation of Methanol and other hydrocarbons Water gas is also called syngas or synthesis gas.

#### Summary

Hydrogen is the third most abundant element on the earth. It constitute 15.4% earth's crust and ocean Isotopes:  Hydrogen has 3- isotopes, they are, 1.Protium (1H1) 2.Deuterium (1H2) 3.Tritium (1H3) The position of hydrogen in the periodic table is debated because it has similar properties like Alkali metals and Halogen. The hydrogen is placed with Alkali metals. The modern periodic table is based on electronic configuration the electronic configuration of Hydrogen is 1s  hence it is placed in First group. Preparation of Dihydrogen: Laboratory preparation of Dihydrogen: 1)  In laboratory it is prepared by the reaction of granulated zinc with dil.Hcl. Zn + 2HCl → ZnCl2 +H2 ↑ 2) Other laboratory method is by the action of metals like Zn, Al on strong alkalis like NaOH or KOH Ex: Zn + 2NaOH → Na2ZnO2 + H2↑ Commercial preparation of Hydrogen:  Hydrogen is prepared by the electrolysis water using Platinum electrode. Here sulphuric acid is used to acidify water. When electric current is passed through water it decomposes to hydrogen and oxygen. Hydrogen gas is released at cathode and oxygen gas is released at anode.         2H2O $\underset{\to }{\text{Electricity}}$  2H2 + O2 Mechanism: H2O ↔ H++OH- At anode: OH- - e- →OH OH+ OH→ H2O + O O + O → O2 ↑ At cathode: H+ + e- → H H + H → H2 ↑ Industrially Hydrogen is prepared by  passing steam over red hot coke or hydrocarbons at high temperature in the presence of Nickel catalyst. The products are CO and Hydrogen.   CH4 + H2O $\underset{\to }{\text{Ni}}$ CO + 3 H2 Water gas:  The mixture of  carbon monoxide and Hydrogen is called water gas(CO + H2)   Water gas is used in the preparation of Methanol and other hydrocarbons Water gas is also called syngas or synthesis gas.

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