Zn(OH)2 is dissolved to form what in strong alkaline solutions?
doc-17344
In weak basic solutions containing Zn2+ ions, the hydroxide Zn(OH)
2 forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([Zn(OH)4]2−). The nitrate Zn(NO3)
2, chlorate Zn(ClO3)
2, sulfate ZnSO
4, phosphate Zn
3(PO4)
2, molybdate ZnMoO
4, cyanide Zn(CN)
2, arsenite Zn(AsO2)
2, arsenate Zn(AsO4)
2·8H
2O and the chromate ZnCrO
4 (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc. One of the simplest examples of an organic compound of zinc is the acetate (Zn(O
2CCH3)
2).
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doc-17343
Binary compounds of zinc are known for most of the metalloids and all the nonmetals except the noble gases. The oxide ZnO is a white powder that is nearly insoluble in neutral aqueous solutions, but is amphoteric, dissolving in both strong basic and acidic solutions. The other chalcogenides (ZnS, ZnSe, and ZnTe) have varied applications in electronics and optics. Pnictogenides (Zn
3N
2, Zn
3P
2, Zn
3As
2 and Zn
3Sb
2), the peroxide (ZnO
2), the hydride (ZnH
2), and the carbide (ZnC
2) are also known. Of the four halides, ZnF
2 has the most ionic character, whereas the others (ZnCl
2, ZnBr
2, and ZnI
2) have relatively low melting points and are considered to have more covalent character.
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doc-7683
In its turn, under anaerobic conditions, the ferrous hydroxide (Fe(OH)
2 ) can be oxidized by the protons of water to form magnetite and molecular hydrogen. This process is described by the Schikorr reaction:
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doc-16711
Salts of many oxidation states of uranium are water-soluble and may be studied in aqueous solutions. The most common ionic forms are U3+ (brown-red), U4+ (green), UO+
2 (unstable), and UO2+
2 (yellow), for U(III), U(IV), U(V), and U(VI), respectively. A few solid and semi-metallic compounds such as UO and US exist for the formal oxidation state uranium(II), but no simple ions are known to exist in solution for that state. Ions of U3+ liberate hydrogen from water and are therefore considered to be highly unstable. The UO2+
2 ion represents the uranium(VI) state and is known to form compounds such as uranyl carbonate, uranyl chloride and uranyl sulfate. UO2+
2 also forms complexes with various organic chelating agents, the most commonly encountered of which is uranyl acetate.
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doc-7660
To avoid the implication of the naked "solvated proton" in solution, acidic aqueous solutions are sometimes considered to contain a less unlikely fictitious species, termed the "hydronium ion" (H
3O+). However, even in this case, such solvated hydrogen cations are more realistically conceived as being organized into clusters that form species closer to H
9O+
4. Other oxonium ions are found when water is in acidic solution with other solvents.
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doc-16700
The most common forms of uranium oxide are triuranium octoxide (U
3O
8) and UO
2. Both oxide forms are solids that have low solubility in water and are relatively stable over a wide range of environmental conditions. Triuranium octoxide is (depending on conditions) the most stable compound of uranium and is the form most commonly found in nature. Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel. At ambient temperatures, UO
2 will gradually convert to U
3O
8. Because of their stability, uranium oxides are generally considered the preferred chemical form for storage or disposal.
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doc-17340
The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed the outer shell s electrons are lost, which yields a bare zinc ion with the electronic configuration [Ar]3d10. In aqueous solution an octahedral complex, [Zn(H
2O)6]2+ is the predominant species. The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of Zn
2Cl
2, a zinc compound with a +1 oxidation state. No compounds of zinc in oxidation states other than +1 or +2 are known. Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.
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doc-17350
Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away. A protective surface layer of oxide and carbonate (Zn
5(OH)
6(CO
3)
2) forms as the zinc corrodes. This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away. The zinc is applied electrochemically or as molten zinc by hot-dip galvanizing or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, lightposts, metal roofs, heat exchangers, and car bodies.
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doc-17355
Zinc chloride is often added to lumber as a fire retardant and can be used as a wood preservative. It is also used to make other chemicals. Zinc methyl (Zn(CH3)
2) is used in a number of organic syntheses. Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints. Crystals of ZnS are used in lasers that operate in the mid-infrared part of the spectrum. Zinc sulfate is a chemical in dyes and pigments. Zinc pyrithione is used in antifouling paints.
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doc-7674
A molecular form called protonated molecular hydrogen (H+
3) is found in the interstellar medium, where it is generated by ionization of molecular hydrogen from cosmic rays. This charged ion has also been observed in the upper atmosphere of the planet Jupiter. The ion is relatively stable in the environment of outer space due to the low temperature and density. H+
3 is one of the most abundant ions in the Universe, and it plays a notable role in the chemistry of the interstellar medium. Neutral triatomic hydrogen H3 can only exist in an excited form and is unstable. By contrast, the positive hydrogen molecular ion (H+
2) is a rare molecule in the universe.
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doc-16714
Uranium carbides and uranium nitrides are both relatively inert semimetallic compounds that are minimally soluble in acids, react with water, and can ignite in air to form U
3O
8. Carbides of uranium include uranium monocarbide (UC), uranium dicarbide (UC
2), and diuranium tricarbide (U
2C
3). Both UC and UC
2 are formed by adding carbon to molten uranium or by exposing the metal to carbon monoxide at high temperatures. Stable below 1800 °C, U
2C
3 is prepared by subjecting a heated mixture of UC and UC
2 to mechanical stress. Uranium nitrides obtained by direct exposure of the metal to nitrogen include uranium mononitride (UN), uranium dinitride (UN
2), and diuranium trinitride (U
2N
3).
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