|
Selenates
The selenate ion is . Selenates are analogous to sulfates and have similar chemistry. They are highly soluble in aqueous solutions at ambient temperatures. Unlike sulfate, selenate is a somewhat good oxidizer; it can be reduced to selenite or selenium. In strongly acidic conditions, the hydrogen selenate ion, , is formed. It corresponds to the selenic acid, H2SeO4, which is a strong acid and can in its concentrated form dissolve gold. The element selenium exhibits several valence states. Selenate is the least reduced, followed by selenite, and elemental selenium; selenide is even more reduced than elemental selenium. The valence state is an important factor to the toxicity of selenium. Selenate is the form required by organisms that need selenium as a micronutrient. These organisms have the ability to acquire, metabolize and excrete selenium. The level at which selenium becomes toxic varies from species to species and is related to other environmental factors like pH ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenic Acid
Selenic acid is the inorganic compound with the formula . It is an oxoacid of selenium, and its structure is more accurately described as . It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.Bernd E. Langner "Selenium and Selenium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. . Structure and bonding The molecule is tetrahedral, as predicted by VSEPR theory. The Se–O bond length is 161 pm. In the solid state, it crystallizes in an orthorhombic structure. Preparation It is prepared by oxidising selenium compounds in lower oxidation states. One method involves the oxidation of selenium dioxide with hydrogen peroxide: : Unlike the production sulfuric acid by hydration of sulfur trioxide, the hydration of selenium trioxide is an impractical method. Instead, selenic acid may also be prepared by the oxidation of selenous acid () with halogens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenite (ion)
Selenite refers to the anion with the chemical formula . It is the oxyanion of selenium. It is the selenium analog of the sulfite ion, . Thus selenite is pyramidal and selenium is assigned oxidation state +4. Selenite also refers to compounds that contains this ion, for example sodium selenite which is a common source of selenite. Selenite also refers to the esters of selenous acid, for example dimethyl selenite . Synthesis and reactions Selenite salts can be prepared by neutralizing solutions of selenous acid, which is generated by dissolving selenium dioxide in water. The process proceeds via the hydrogenselenite ion, . Most selenite salts can be formed by heating the metal oxide with selenium dioxide, e.g.: : References [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Selenate
Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula , called dihydrogen, or sometimes hydrogen gas, molecular hydrogen, or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas (dihydrogen) and in molecular forms, such as in water and organic compounds. The most common isotope of hydrogen (H) consists of one proton, one electron, and no neutrons. Hydrogen gas was first produced artificially in the 17th century by the reaction of acids with metals. Henry Cavendish, in 1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned; hence its name means 'water-f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
