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HYDROGEN

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					HYDROGEN

  Laura Vidal Juan
                  INTRODUCTION
• Etymology: the name of an element.
• Hydrogen is the chemical element with atomic number 1. It
  is represented by the symbol H.




• Its atomic mass is 1.00794 amu (hydrogen is the lightest
  element).
• Hydrogen is the most abundant of the chemical elements,
  constituting roughly 75% of the universe's elemental mass
• Elemental hydrogen is relatively rare on Earth, and is
  industrially produced from hydrocarbons
                       DISCOVERY
• T. Von Hohenheim = Paracelsus (1493–1541) produced H2
  artificially via the mixing of metals with strong acids.
• Robert Boyle (1671) rediscovered and described the reaction
  between iron filings and dilute acids, which results in the production
  of hydrogen gas.
• Henry Cavendish (1766) recognized hydrogen gas as a discrete
  substance, by identifying the gas from a metal-acid reaction as
  "inflammable air" and further finding that the gas produces water
  when burned.
• Antoine Lavoisier (1783) gave the element the name of hydrogen
  when he (with Laplace) reproduced Cavendish's finding.
• Study of the energetics and bonding of the hydrogen atom by
  Maxwell, has played a key role in the development of quantum
  mechanics.
               COMPOUNDS

• Bonded to fluorine, oxygen, or
  nitrogen it forms hydrogen bonding.
• With metals and metalloids it forms
  hydrides, that could be implied in
  coordination complex.
• With carbon it forms organic
  compounds: importance in
  Biochemistry.
• H+ is implied in acid-base chemistry.
                 BIOHYDROGEN
• H2 is a product of some types of anaerobic metabolism and it is
  produced by several microorganisms.

• It take part in redox reactions
  (hydrogenases).

• H2 is created during pyruvate fermentation to water.

• Water splitting, that occurs during photosintesis, give rise to H+.

• H+ is important in the electronic transfer chain.
CHEMICAL CHARACTERISTICS
• Hydrogen is highly soluble in many compounds of rare
  earth metals and transition metals and can be dissolved
  in crystalline and amorphous metals.
• It is highly flammable and will burn at concentrations as
  low as 4% H2 in air.
• It ignites automatically at a temperature of 560 °C.
• H2 reacts directly with other oxidizing elements.
• Pure hydrogen-oxygen flames burn in the ultraviolet
  color range and are nearly invisible to the naked eye.
                  SOME PROPERTIES
 General: At standard temperature and pressure, hydrogen is a
  colorless, odorless, nonmetallic, tasteless, highly flammable
  diatomic gas with the molecular formula H2.

 Physical properties:
 Density = 0.08988 g/L           Heat of fusion = 117 kJ·mol−1
 Melting point = 14.01 K         Heat of vaporization = 0.904 kJ·mol−1
 Boiling point = 20.28 K         It has the highest thermal conductivity of any gas


 Atomic properties:
 Crystal structure = hexagonal
 Atomic radius = 25 pm
 Electronegativity = 2.1
                     APPLICATIONS I
• One of the first uses of H2 was for balloons, and later airships.
  Infamously, H2 was used in the Hindenburg airship that was
  destroyed in a midair fire.

   The highly flammable hydrogen (H2) was later
   replaced for airships and most balloons by the
   unreactive helium (He).


• Uses in petroleum and chemical industries: processing of fossil fuels, and in
  the production of ammonia.

• Uses as a reactant: hydrogenating agent (in increasing the level of saturation
  of unsaturated fats and oils ); in the production of methanol; in the
  manufacture of hydrochloric acid; reducing agent of metallic ores.
           APPLICATIONS II
• Applications in physics and engineering: shielding gas in
  welding methods, the rotor coolant in electrical generators
  at power stations
• Liquid H2 is used in cryogenic research
• As a tracer gas for minute leak detection
• Isotopes: Protium is the most common isotope; Deuterium
  (hydrogen-2) is used in nuclear fission application; Tritium
  (hydrogen-3), produced in nuclear reactors, is used in the
  production of hydrogen bombs, as an isotopic label in the
  biosciences, and as a radiation source in luminous paints.

				
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posted:9/10/2011
language:English
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