Hydrogen

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Hydrogen
Chemical formula H
Atomic Number
OTP appearance colorless gas 
Molar Mass(g/mol)
Melting Point(°C) -260 
Boiling Point(°C) -253 
Density(g/cc) 0.00009 
Fuel Value(MJ/kg) 120.21 
Speed of sound
20°C, 1atm (m/s)
1270
NFPA 704
NFPA704.png
4
0
0
 

Uses

Justification Questioned

Secondary

  • As a fuel
  • As a lifting gas

Natural Sources

  • Elemental hydrogen does occur naturally in the ionosphere, but is not accessible in general
  • Hydrogen occurs naturally in water and virtually all acids

Hazards

The bond energy released when hydrogen is produced is often sufficient to ignite it if it comes into contact with oxygen. Be careful.

Production

Elemental Hydrogen

Berthelot

In an oxygen-free environment, forcing water or steam into a red-hot iron tube results in hydrogen gas exiting the system:

3 Fe + 4 H2O Fe3O4 + 4 H2

Electrolysis

2 H2O 2 H2 + O2 ; Catalyzed by various salts including (Co,Fe)P4N2

Metal reactivity series

acid
alkali
  • Aqueous sodium hydroxide and aluminum react to produce hydrogen gas. This should be done in an oxygen free environment to prevent the heat of the reaction from igniting the hydrogen.
    2 Al + 2 NaOH + 2 H2O 2 NaAlO2 + 3 H
water

See Also