Laboratory and Industrial preparation of hydrogen - Physical and Chemical properties of hydrogen

Laboratory and Industrial preparation of hydrogen - Physical properties of hydrogen

Contents:

- Preparation of Hydrogen (laboratory and industrial preparation of hydrogen)

- Physical  properties of hydrogen

- Chemical properties of hydrogen

Preparation of Hydrogen (laboratory and industrial preparation of hydrogen):

There are number of methods to synthesize hydrogen gas including the laboratory and industrial preparation of hydrogen.

   1. Hydrogen gas can be prepared from carbon. This method is the commercial preparation of hydrogen. The preparation involves passing steam over red hot coke. The product is water gas, which is a mixture of CO and H₂.

     The CO liquefied at low temperature under pressure, thus separating it from H₂.

 

    2.From light hydrocarbons such as methane are mixed with steam and passed over a nickel catalyst at 800-900 ^oC. this method is very important method for industrial preparation of hydrogen.

 

    3. Very pure hydrogen (99.9% pure) is made by electrolysis of water or solutions of NaOH or KOH. In this method hydrogen is evolved at cathode.

 

 

    4. A large amount of pure hydrogen is also formed as a byproduct from the chlor-alkali industry, in which aqueous NaCl is electrolyzed to produce NaOH, Cl₂ and H₂. This method is useful for hydrogen production.

 

    5. The usual laboratory preparation of hydrogen is the reaction of dilute acids with metals, or of an alkali with aluminum as in the following balanced equation.

     6.Hydrogen can be prepared by the reaction of salt-like hydrides with water.

Physical properties of hydrogen (Properties of Molecular Hydrogen):

• Hydrogen is the lightest gas known. It is colorless, odorless and almost insoluble in water. 
• Hydrogen is not very reactive under normal conditions. Consequently hydrogen reactions are slow, or require high temperatures, or catalysts.
• Many important reactions of hydrogen involve the catalysts which first reacts with H₂ and either breaks or weakens the H-H bond and thus lowers the activation energy. Examples include:

1. The Haber process for the manufacture of NH₃ from H₂ using a catalyst of activated Fe at 380-450 ^oC and 200 atmospheres pressure. 
2. The hydrogenation of a variety of unsaturated organic compounds use Ni, Pd or Pt as catalysts.
3. The production of methanol by reducing CO with H₂over a Cu-Zn catalyst at 300°C.

      See Also:

Isotopes of hydrogen
Chemical bonding
Types of Hydrogen
 

Chemical properties of hydrogen (Reactions of Hydrogen)

(1) Reaction with Oxygen:

Hydrogen burns in air or oxygen, forming water, and liberates a large amount of energy. This is used in the oxy-hydrogen flame for welding and cutting metals. 

(2) Reaction with Halogens:

The reaction with fluorine is violent. The reaction with chlorine is slow in the dark, but the reaction is catalyzed by light (photo catalysis). 

(3) Haber Process:

Large quantities of H₂ are used in the industrial production of ammonia by the Haber process.

 

Types of Hydrogen (Ortho and Para Hydrogen):

 

§  In hydrogen molecule H₂, the direction of spin of hydrogen nucleus gives spin isomerism. Therefore, H₂ exists in two different forms known as ortho and para hydrogen.

 

§  Ortho Hydrogen: The two nuclei spin in the same direction

§   Para Hydrogen The two nuclei spin in the opposite direction.

 

§  The para form has the lower energy, and the more stable form of hydrogen.