化学专业英语之副族元素
GROUPS IB AND IIB ELEMENTS刹车有异响
Physical properties of Group IB and IIB
The elements have a greater bulk u as metals than in compounds, and their physical properties vary widely.
Gold is the most malleable and ductile of the metals. It can be hammered into sheets of 0.00001 inch in thickness; one gram of the metal can be drawn into a wire 1.8 mi in length1. Copper and silver are also metals that are mechanically easy to work. Zinc is a little brittle at ordinary temperatures, but may be rolled into sheets at between 120° to 150℃; it becomes brittle again about 200℃-The low-melting temperatures of zinc contribute to the preparation of zinc-coated iron .galvanized iron; clean iron sheet may be dipped into vats of liquid zinc in its preparation. A different procedure is to sprinkle or air blast zinc dust onto hot iron sheeting for a zinc melt and then coating.
Cadmium has specific us becau of its low-melting temperature in a number of alloys. Cadmium rods are ud in nuclear reactors becau the metal is a good neutron absorber.
Mercury vapor and its salts are poisonous, though the free metal may be taken internally under certain conditions. Becau of its relatively low boiling point and hence volatile nature, free mercury should never be allowed to stand in an open container in the laboratory. Evidence shows that inhalation of its vapors is injurious.
The metal alloys readily with most of the metals (except iron and platinum) to form amalgams, the name given to any alloy of mercury.
Copper sulfate, or blue vitriol (CuSO4 • 5H2O) is the most important and widely ud salt of copper. On heating, the salt slowly los water to form first the trihydrate (CuSO4 • 3HzO), then the monohydrate (CuSO4 • H2一个字诠释重生O), and finally the white anhydrous salt. The anhydrous salt is often ud to test for the prence of water in organic liquids. For example, some of the anhydrous copper salt added to alcohol (which contains water) will
turn blue becau of the hydration of the salt.
Copper sulfate is ud in electroplating. Fishermen dip their nets in copper sulfate solution to inhibit the growth of organisms that would rot the fabric. Paints specifically formulated for u on the bottoms of marine craft contain copper compounds to inhibit the growth of barnacles and other organisms.
When dilute ammonium hydroxide is added" to a solution of copper (I) ions, a greenish precipitate of Cu(OH)2 or a basic copper(I) salt is formed. This dissolves as more ammonium hydroxide is added. The excess ammonia forms an ammoniated complex with the copper (I) ion of the composition, Cu(NH3)42+. This ion is only slightly dissociated; hence in an ammoniacal solution very few copper (I) ions are prent. Insoluble copper compounds, execpt copper sulfide, are dissolved by ammonium hydroxids. The formation of the copper (I) ammonia ion is often ud as a test for Cu2+ becau of its deep, inten blue color.
Copper (I) ferrocyanide [女性腋下疼痛Cu2Fe(CN)6] is obtained as a reddish-brown precipitate on the addition of a soluble ferrocyanide to a solution of copper ( I )ions. The formation of this salt is also ud as a test for the prence of copper (I) ions.
Compounds of Silver and Gold
Silver nitrate, sometimes called lunar caustic, is the most important salt of silver. It melts readily and may be cast into sticks for u in cauterizing wounds. The salt is prepared by dissolving silver in nitric acid and evaporating the solution.
3Ag + 4HN初级职称证书O3—3AgNO3 + NO + 2H2O
The salt is the starting material for most of the compounds of silver, including the halides ud in photography. It is readily reduced by organic reducing agents, with the formation of a black deposit of finely divided silver; this action is responsible for black spots left on the fingers from the handling of the salt. Indelible marking inks and pencils take advantage of this property of silver nitrate.
The halides of silver, except the fluoride, are very insoluble compounds and may be precipitated by the addition of a solution of silver salt to a solution containing chloride, bromide, or iodide ions.什么闻什么睹的成语
The addition of a strong ba to a solution of a silver salt precipitates brown silver oxide (Ag2G). One might expect the hydroxide of silver to precipitate, but it ems likely that silver hydroxide is very unstable and breaks down into the oxide and water — if, indeed, it is ever formed at all3. However, since a solution of silver oxide js definitely basic, there must be hydroxide ions prent in solution.
Ag2O + H2O = 2Ag+ + 2OH网店推广方案-
Becau of its inactivity, gold forms relatively few compounds. Two ries of compounds are known — monovalent and trivalent. Monovalent (aurous) compounds remble silver compounds (aurous chloride is water insoluble and light nsitive), while the higher valence (auric) compounds tend to form complexes. Gold is resistant to the action of mos
t chemicals —air, oxygen, and water have no effect. The common acids do not attack the metal, but a mixture of hydrochloric and nitric acids (aqua regia) dissolves it to form gold( I ) chloride or chloroauric acid. The action is probably due to free chlorine prent in the aqua regia.
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