Bạn đang xem: C4h8 + br2
Corrections? Updates? Omissions? Let us know if you have suggestions lớn improve this article (requires login).
Feedback TypeSelect a type (Required)Factual CorrectionSpelling/Grammar CorrectionLink CorrectionAdditional InformationOther
Our editors will nhận xét what you’ve submitted and determine whether khổng lồ revise the article.
Join magmareport.net"s Publishing Partner Program and our community of experts to gain a global audience for your work!While every effort has been made to follow citation style rules, there may be some discrepancies.Please refer to lớn the appropriate style manual or other sources if you have any questions.
Corrections? Updates? Omissions? Let us know if you have suggestions to lớn improve this article (requires login).
Feedback TypeSelect a type (Required)Factual CorrectionSpelling/Grammar CorrectionLink CorrectionAdditional InformationOther
Our editors will reviews what you’ve submitted và determine whether khổng lồ revise the article.
Join magmareport.net"s Publishing Partner Program và our community of experts to lớn gain a global audience for your work!
Key People:Antoine-Jérôme BalardViktor Meyer...(Show more)Related Topics:chemical elementhalogen...(Show more)
bromine (Br), chemical element, a deep red noxious liquid, & a member of the halogen elements, or Group 17 (Group VIIa) of the periodic table.
| 35 |
| <79.901, 79.907> |
| −7.2 °C (19 °F) |
| 59 °C (138 °F) |
| 3.12 at đôi mươi °C (68 °F) |
| −1, +1, +3, +5, +7 |
| (Ar)3d104s24p5 |
History
Bromine was discovered in 1826 by the French chemist Antoine-Jérôme Balard in the residues (bitterns) from the manufacture of sea salt at Montpellier. He liberated the element by passing chlorine through an aqueous solution of the residues, which contained magnesium bromide. Distillation of the material with manganese dioxide and sulfuric acid produced red vapours, which condensed to a dark liquid. The similarity of this procedure khổng lồ that for making chlorine suggested khổng lồ Balard that he had obtained a new element similar lớn chlorine. (The German chemist Justus von Liebig appears to have obtained the element before Balard, but he wrongly considered it to be iodine chloride.) Because of the bad odour of the element, the French Academy of Sciences suggested the name bromine, from the Greek word bromos, meaning “bad smell” or “stench.”
Occurrence và distribution
A rare element, bromine is found in nature dispersed throughout Earth’s crust only in compounds as soluble và insoluble bromides. Some enrichment occurs in ocean water (65 parts per million by weight), in the Dead Sea (approximately 5 grams per litre <0.7 ounce per gallon>), in some thermal springs, và in rare insoluble silver bromide minerals (such as bromyrite, found in Mexico and Chile). Natural salt deposits và brines are the main sources of bromine and its compounds. Jordan, Israel, China, và the United States led the world in bromine production in the early 21st century; other important bromine-producing countries during that period include Japan, Ukraine, & India.
Natural bromine is a mixture of two stable isotopes: bromine-79 (50.54 percent) & bromine-81 (49.46 percent). Of the 17 known radioactive isotopes of the element, bromine-77 has the longest half-life (57 hours).
Physical & chemical properties
Free bromine is a reddish brown liquid with an appreciable vapour pressure at room temperature. Bromine vapour is amber in colour. Bromine has a pungent odour và is irritating lớn the skin, eyes, và respiratory system. Exposure lớn concentrated bromine vapour, even for a short time, may be fatal. Like the other halogens, bromine exists as diatomic molecules in all aggregation states.
About 3.41 grams (0.12 ounce) of bromine dissolve in 100 millilitres (0.1 quart) of water at room temperature. The solution is known as bromine water. Like chlorine water, it is a good oxidizing agent, và it is more useful because it does not decompose so readily. It liberates không tính tiền iodine from iodide-containing solutions & sulfur from hydrogen sulfide. Sulfurous acid is oxidized by bromine water to lớn sulfuric acid. In sunlight bromine water decomposes, with release of oxygen, as in the following equation:
Get a magmareport.net Premium subscription and gain access to exclusive content. Subscribe Now
From bromine water a hydrate (a clathrate) can be isolated that contains 172 water molecules and 20 cavities capable of accommodating the bromine molecules. Bromine dissolves in aqueous alkali hydroxide solutions, giving bromides, hypobromites, or bromates, depending on the temperature. Bromine is readily extracted from water by organic solvents such as carbon tetrachloride, chloroform, or carbon disulfide, in which it is very soluble. In the organic solvents it gives an orange solution.
The electron affinity of bromine is high and is similar to lớn that of chlorine. It is, however, a less powerful oxidizing agent, chiefly because of the weaker hydration of the bromide ion as compared with the chloride ion. Similarly, a metal-bromine bond is weaker than the corresponding metal-chlorine bond, & this difference is reflected in the chemical reactivity of bromine, which lies between that of chlorine and that of iodine. An organic bromo compound resembles the corresponding chloro derivative but is usually more dense, less volatile, less combustible, và less stable.
Bromine combines violently with the alkali metals và with phosphorus, arsenic, aluminum, và antimony but less violently with certain other metals. Bromine displaces hydrogen from saturated hydrocarbons and adds lớn unsaturated hydrocarbons, though not as readily as chlorine does.
The most stable oxidation state of the element is −1, in which bromine occurs naturally. But oxidation states of 0 (elemental bromine, Br2), +1 (hypobromite, BrO−), +3 (bromite, BrO−2), +5 (bromate, BrO−3), and +7 (perbromate, BrO−4) are also known. The first ionization energy of bromine is high, và compounds containing bromine in positive oxidation numbers are stabilized by appropriate ligands, mainly oxygen & fluorine. Compounds with the oxidation numbers +1, +3, +4, +5, & +7 all contain covalent bonds.
Production and use
The chief commercial source of bromine is ocean water, from which the element is extracted by means of chemical displacement (oxidation) by chlorine in the presence of sulfuric acid through the reaction
The sản phẩm of the reaction is a dilute solution of bromine, from which the element is removed by blowing air through it. The không tính tiền bromine is then mixed with sulfur dioxide, & the mixed gases are passed up a tower down which water is trickling. The following reaction takes place in the tower:
resulting in a mixture of acids that is much richer in bromide ion than seawater. A second treatment with chlorine liberates bromine, which is freed from chlorine và purified by passage over moist iron filings.
Commercial bromine generally contains up lớn 0.3 percent chlorine. It is usually stored in glass bottles or in barrels coated with lead or Monel metal.
The industrial usage of bromine had been dominated by the compound ethylene bromide (C2H4Br2), which once was added to lớn gasoline with tetraethyl lead lớn prevent deposition of lead in the engine. Since the renunciation of leaded gasoline, bromine compounds have mainly been used in flame retardants, but ethylene bromide is still an important compound because of its use lớn destroy nematodes & other pests in soils. Bromine is also used in the production of catalysts, such as aluminum bromide.
Xem thêm: Văn Mẫu Bài Tập Làm Văn Số 5 Đề 4, Mẫu Bài Viết Số 5 Lớp 7 Đầy Đủ 5 Đề
Bromine has other uses, as in making various dyes & the compounds tetrabromoethane (C2H2Br4) & bromoform (CHBr3), which are used as liquids in gauges because of their high specific gravity. Until the development of barbiturates in the early 20th century, bromides of potassium, sodium, calcium, strontium, lithium, & ammonium were used widely in medicine because of their sedative action. Silver bromide (AgBr), an important component of photographic film, is, lượt thích silver chloride and iodide, light sensitive. Traces of potassium bromate (KBrO3) are added lớn wheat flour lớn improve baking. Other bromine compounds of significance include hydrogen bromide (HBr), a colourless gas used as a reducing agent và a catalyst in organic reactions. A solution of the gas in water is called hydrobromic acid, a strong acid that resembles hydrochloric acid in its activity toward metals and their oxides and hydroxides.