CHLORINE


A. Characteristic

An : 17
N : 18
Am : 35.453 g/mol
Group No : 17
Group Name : Halogen
Block : p-block
Period : 3
State : gas at 298 K
Colour : yellowish green
Classification : Non-metallic
Boiling Point : 239.1K (-34.04oC)
Melting Point : 172.16K (-101.5oC)
Density : 3.2g/l

B. Discovery Information

Who : Karl Wilhelm Scheele
When : 1774
Where : Sweden

C. Name Origin

Greek : khloros (green).
"Chlorine" in different languages.

D. Sources

Never found in free form in nature. Salt (sodium chloride, NaCl) is its most common compound. Chlorides make up much of the salt dissolved in the Earth’s oceans - about 1.9% of the mass of seawater is chloride ions.

E. Abundance

Universe : 1 ppm
Sun : 8 ppm
Earth’s Crust : 130 ppm
Seawate r: 18000 ppm
Human : 1.2 x 106 ppb by weight; 2.1 x 105 ppb by atoms

F. Uses

Used widely in paper product production, antiseptic, dyestuffs, food, insecticides, paints, petroleum products, plastics, medicines, textiles, solvents, and many other consumer products. Chlorine is an important chemical in some processes of water purification, disinfectants and in bleaches and chlorofluorocarbons (CFC).

G. Notes

The pure chemical element has the physical form of a diatomic yellow-green gas, Cl2. Chlorine combines readily with nearly all other elements. Chlorine is about two and a half times as heavy as air. Chlorine gas was first used as weapon against human beings in World War I on April 22nd, 1915.

H. Hazards

Chlorine irritates respiratory systems especially in children and the elderly. In its gaseous state it irritates mucous membranes and in its liquid state it burns skin. As little as 3.5 ppm (parts per million) can be detected as an odour, and 1000 ppm is likely to be fatal after a few deep breaths. Toxic fumes may be produced when bleach is mixed with urine, ammonia (NH3), hydrochloric acid (HCl), or another cleaning product. These fumes consist of a mixture of chlorine gas, chloramine and nitrogen trichloride; therefore these combinations should be avoided.

I. Reactions of Chlorine

1. Reactions with water
Chlorine reacts with water to produce hypochlorite, OCl-. The pH of the solution determines the position of the equilibrium.
Cl2(g) + H2O(l) <=> OCl-(aq) + 2H+(aq) + Cl-(aq)
2. Reactions with air
Chlorine is not reacive towards nitrogen or oxygen.
3. Reactions with halogens
Fluorine reacts with chlorine at 225oC to form the interhalogen species ClF. The trifluoride chlorine(III) fluoride is also formed if the reaction does not go to completion.
Cl2(g) + F2(g) --> 2ClF(g)
Cl2(g) + 3F2(g) --> 2ClF3(g)
Under more forcing conditions, excess fluorine reacts with chlorine at 350oC and 225 atmospheres pressure to form the interhalogen species ClF5.
Cl2(g) + 5F2(g) --> 2ClF5(g)
Chlorine, reacts with bromine in the gas phase to form the unstable interhalogen species bromine(I)chloride, ClBr.
Cl2(g) + Br2(g) --> 2ClBr(g)
Chlorine reacts with iodine at room temperature to form the interhalogen species iodine(I)chloride, ClI.
Cl2(g) + I2(s) --> 2ICl(s)
4. Reactions with bases
Chlorine reacts with hot aqueous alkali to produce chlorate, ClO3-. Only one sixth of the total chlorine is converted in this reaction.
3Cl2(g) + 6OH-(aq) --> ClO3-(aq) + 5Cl-(aq) + 3H2O

J. Chlorine Compounds

1. Calcium hypochlorite Ca(ClO)2
It is widely used for water treatment (drinking water or swimming pools) and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).
2. Hydrochloric acid HCl (Highly corrosive)
Hydrochloric acid is a strong inorganic acid that is used in many industrial processes. The largest hydrochloric acid consumption is in the production of organic compounds such as vinyl chloride for PVC, and MDI and TDI for polyurethane. This is often captive use, consuming locally-produced hydrochloric acid that never actually reaches the open market. Other organic compounds produced with hydrochloric acid include bisphenol A for polycarbonate, activated carbon, and ascorbic acid, as well as numerous pharmaceutical products.
Hydrochloric acid is a fundamental chemical, and as such it is used for a large number of small-scale applications, such as leather processing, household cleaning, and building construction. In addition, a way of stimulating oil production is by injecting hydrochloric acid into the rock formation of an oil well, dissolving a portion of the rock, and creating a large-pore structure. Oil-well acidizing is a common process in the North Sea oil production industry.
Many chemical reactions involving hydrochloric acid are applied in the production of food, food ingredients, and food additives. Typical products include aspartame, fructose, citric acid, lysine, hydrolyzed (vegetable) protein as food enhancer, and in gelatin production. Food-grade (extra-pure) hydrochloric acid can be applied when needed for the final product. Mixing simple aluminium foil with hydrochloric acid produces hydrogen. The hydrogen can then be stored in a balloon. Upon application of a flame to the balloon it will produce a fiery explosion.
3. Chlorine dioxide ClO2 (Oxidizer, Highly Toxic)
A reddish-yellow gas which is one of several known oxides of chlorine. Chlorine dioxide is not stable in the gas state above 15% volume in air at STP and can spontaneously and explosively decompose into chlorine and oxygen.
Chlorine dioxide is used primarily (95% +) for bleaching of wood pulp, but is also used for the bleaching of flour and for the disinfection of water. Chlorine dioxide is also used in conjunction with ozone disinfection of water to reduce the formation of bromates which are regulated carcinogens.
It is more effective than chlorine against viruses, bacteria and protozoa.
4. Natrium Chloride NaCl
Natrium chloride, also known as common salt, table salt, or halite. Natrium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. It is essential to life on Earth. Most biological tissues and body fluids contain a varying amount of salt. The concentration of sodium ions in the blood is directly related to the regulation of safe body-fluid levels. Propagation of nerve impulses by signal transduction is regulated by sodium ions. (Potassium, a metal closely related to Sodium, is also a major component in the same bodily systems).
5. Natrium hypochlorite NaOCl
A solution of sodium hypochlorite is frequently used as a disinfectant and as a bleaching agent; indeed, often it is simply called "bleach", though other chemicals are sometimes given that name as well.

K. Isotopes of Chlorine

35Cl [18 neutrons]
Abundance : 75.77%
Stable with 18 neutrons
36Cl [19 neutrons]
Abundance : synthetic
Half life : 3.01 x 105 years [ beta- ]
Decay Energy : 0.709MeV
Decays to 36Ar.
Half life : 3.01 x 105 years [ Electron Capture ]
Decay Energy : unknownMeV
Decays to 36S.
37Cl [20 neutrons]
Abundance : 24.23%
Stable with 20 neutrons
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