Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's chemical elemental mass. In normal conditions it’s a colourless, odourless and insipid gas, formed by diatomic molecules, H2.
Stars in the main sequence are mainly composed of hydrogen in its plasma state. Naturally occurring elemental hydrogen is relatively rare on Earth. It found as the main compounds of water and of all organic matter, and it’s widely spread not only on Earth but also in the entire Universe.
There are three hydrogen isotopes: protium, mass 1, found in more than 99,985% of the natural element; deuterium, mass 2, found in nature in 0.015% approximately, and tritium, mass 3, which appears in small quantities in nature, but can be artificially produced by various nuclear reactions.
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[edit] History
Hydrogen gas (now known to be H2) was first artificially produced in the early 16th century, via the mixing of metals with strong acids. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, a property which later gave it its name, which in Greek means "water-former."
[edit] Extraction
Hydrogen can be extracted from several different fuels:
[edit] The Classics:
Natural gas, Gasoline, diesel gas and propane all contain massive amounts of hydrogen that can be used in a fuel cell.
[edit] Green Gas
Renewable gasses and fuels also offer hydrogen, these fuels can be ethanol, methanol, landfill gas, bio-gas, and methane.
[edit] Water
Water is two thirds hydrogen, and the most abundant molecule on Earth. Through electrolysis, the oxygen and hydrogen can be separated and put to use.
[edit] Exotic
There are very exotic forms of hydrogen fuel, these include peanut shells, algae, and sodium borohydride (highly corrosive, toxic, flammable, and highly water-reactive compound).
Additionally, industrial production is mainly from the steam reforming of natural gas, and less often from more energy-intensive hydrogen production methods like the electrolysis of water. Most hydrogen is employed near its production site, with the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market.
[edit] Uses
The most important use of hydrogen is the ammonia synthesis. The use of hydrogen is extending quickly in fuel refinement, like the breaking down by hydrogen (hydrocracking), and in sulphur elimination. Huge quantities of hydrogen are consumed in the catalytic hydrogenation of unsaturated vegetable oils to obtain solid fat. Hydrogenation is used in the manufacture of organic chemical products. Huge quantities of hydrogen are used as rocket fuels, in combination with Oxygen or fluor, and as a rocket propellent propelled by nuclear energy.
Hydrogen can be burned in internal combustion engines. Hydrogen fuel cells are being looked into as a way to provide power and research is being conducted on hydrogen as a possible major future fuel. For instance it can be converted to and from electricity from bio-fuels, from and into natural gas and diesel fuel, theoretically with no emissions of either CO2 or toxic chemicals.
[edit] Properties
At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustible diatomic gas with the molecular formula H2. It is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume
Hydrogen reacts with every oxidizing element and can react spontaneously and violently at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially dangerous acids.
Pure hydrogen-oxygen flames emit ultraviolet light and are nearly invisible to the naked eye. The detection of a burning hydrogen leak may require a flame detector; such leaks can be very dangerous.
Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks.
Common hydrogen has a molecular weight of 2,01594 g. As a gas it has a density of 0.071 g/l at 0ºC and 1 atm. Its relative density, compared with that of the air, is 0.0695. Hydrogen is the most flammable of all the known substances. Hydrogen is slightly more soluble in organic solvents than in water. Many metals absorb hydrogen. Hydrogen absorption by steel can result in brittle steel, which leads to fails in the chemical process equipment.
At normal temperature hydrogen is a not very reactive substance, unless it has been activated somehow; for instance, by an appropriate catalyser. At high temperatures it’s highly reactive.
Although in general it’s diatomic, molecular hydrogen dissociates into free atoms at high temperatures. Atomic hydrogen is a powerful reductive agent, even at ambient temperature. It reacts with the oxides and chlorides of many metals, like silver, copper, lead, bismuth and mercury, to produce free metals. It reduces some salts to their metallic state, like nitrates, nitrites and sodium and potassium cyanide. It reacts with a number of elements, metals and non-metals, to produce hydrides, like NAH, KH, H2S and PH3. Atomic hydrogen produces hydrogen peroxide, H2O2, with oxygen.
Atomic hydrogen reacts with organic compounds to form a complex mixture of products; with etilene, C2H4, for instance, the products are ethane, C2H6, and butane, C4H10. The heat released when the hydrogen atoms recombine to form the hydrogen molecules is used to obtain high temperatures in atomic hydrogen welding.
Hydrogen reacts with Oxygen to form water and this reaction is extraordinarily slow at ambient temperature; but if it’s accelerated by a catalyser, like platinum, or an electric spark, it’s made with explosive violence.
[edit] Health effects of hydrogen
[edit] Effects of exposure to hydrogen:
[edit] Fire:
Extremely flammable. Many reactions may cause fire or explosion.
[edit] Explosion:
Gas/air mixtures are explosive.
[edit] Routes of exposure:
The substance can be absorbed into the body by inhalation. Inhalation: High concentrations of this gas can cause an oxygen-deficient Environment. Individuals breathing such an atmosphere may experience symptoms which include headaches, ringing in ears, dizziness, drowsiness, unconsciousness, nausea, vomiting and depression of all the senses. The skin of a victim may have a blue color. Under some circumstances, death may occur. Hydrogen is not expected to cause mutagenicity, embryotoxicity, teratogenicity or reproductive toxicity. Pre-existing respiratory conditions may be aggravated by overexposure to hydrogen.
[edit] Inhalation risk:
On loss of containment, a harmful concentration of this gas in the air will be reached very quickly.
[edit] Physical dangers:
The gas mixes well with air, explosive mixtures are easily formed. The gas is lighter than Air.
[edit] Chemical dangers:
Heating may cause violent combustion or explosion. Reacts violently with air, oxygen, halogens and strong oxidants causing fire and explosion hazard. Metal catalysts, such as platinum and nickel, greatly enhance these reactions.
High concentrations in the air cause a deficiency of oxygen with the risk of unconsciousness or death. Check oxygen content before entering area. No odor warning if toxic concentrations are present. Measure hydrogen concentrations with suitable gas detector (a normal flammable gas detector is not suited for the purpose).
[edit] First aid:
Fire: Shut off supply; if not possible and no risk to surroundings, let the fire burn itself out. In other cases extinguish with water spray, powder, Carbon dioxide.
[edit] Explosion:
In case of fire: keep cylinder cool by spraying with water. Combat fire from a sheltered position.
[edit] Inhalation:
Fresh air, rest. Artificial respiration may be needed. Refer for medical attention. Same for skin, refer for medical attention.
[edit] Hydrogen (H2) Applications and Uses:
[edit] Metals:
Hydrogen is mixed with inert gases to obtain a reducing atmosphere, which is required for many applications in the metallurgical industry, such as heat treating steel and welding. It is often used in annealing stainless steel alloys, magnetic steel alloys, sintering and copper brazing.
Hydrogen can be produced by dissociation of ammonia at about 1800˚F with the aid of a catalyst - which results in a mix of 75% hydrogen and 25% mononuclear nitrogen (N rather than N2). The mix is used as a protective atmosphere for applications such as brazing or bright annealing.
[edit] Chemicals, Pharmaceuticals and Petroleum:
Hydrogen is used in large quantities as a raw material in the chemical synthesis of Ammonia, Methanol, hydrogen peroxide, polymers, and solvents.
In refineries, it is used to remove the Sulfur that contained in crude oil. Hydrogen is catalytically combined with various intermediate processing streams and is used, in conjunction with catalytic cracking operations, to convert heavy and unsaturated compounds to lighter and more stable compounds.
The pharmaceutical industry uses hydrogen to manufacture Vitamins and other pharmaceutical products.
Large quantities of hydrogen are used to purify gases (e.g. argon) that contain trace amounts of oxygen, using catalytic combination of the oxygen and hydrogen followed by removal of the resulting water.
[edit] Glass and Ceramics:
In float glass manufacturing, hydrogen is required to prevent oxidation of the large tin bath.
[edit] Food and Beverages:
It is used to hydrogenate unsaturated fatty acids in animal and vegetable oils, producing solid Fats for margarine and other food products.
[edit] Electronics:
Hydrogen is used as a carrier gas for such active trace elements as arsine and phospine, in the manufacture of semi-conducting layers in integrated circuits.
[edit] Miscellaneous:
Generators in large power plants are often cooled with hydrogen, since the gas processes high thermal conductivity and offers low friction resistance.
Liquid hydrogen is used as a rocket fuel.
The nuclear fuel industry uses hydrogen as a protective Atmosphere in the fabrication of fuel rods.
[edit] Environmental effects of hydrogen
[edit] Hydrogen in the environment:
Hydrogen forms 0.15 % of the Earth's crust, it is the major constituent of water. 0.5 ppm of hydrogen H2 and varial proportions as water vapour are present in the Atmosphere. Hydrogen is also a majosr component of Biomass, constituting the 14% by weight.
[edit] Environmental stability:
Hydrogen occurs naturally in the atmosphere. The gas will be dissipated rapidly in well-ventilated areas.
[edit] Effect on plants or animals:
Any effect on animals would be related to oxygen deficient environments. No adverse effect is anticipated to occur to plant life, except for frost produced in the presence of rapidly expanding gases.
[edit] Effect on aquatic life:
No evidence is currently available on the effect of hydrogen on aquatic life.
