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Chromium(II) Oxide
Chromium(II) oxide (CrO) is an inorganic compound composed of chromium and oxygen. It is a black powder that crystallises in the rock salt structure.Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide: : H3PO2 + 2 Cr2O3 → 4 CrO + H3PO4 It is readily oxidized by the atmosphere. CrO is basic, while is acidic, and is amphoteric.Chemistry 7th edition, by Raymond Chang page 645 (problem 15.100) See also * Chromium(IV) oxide * Chromium(VI) oxide Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple s ... References Chromium(II) compounds Transition metal oxides Reducing agents Chromium–oxygen compounds Rock salt crystal structure {{inorganic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cubic Crystal System
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of these crystals: *Primitive cubic (abbreviated ''cP'' and alternatively called simple cubic) *Body-centered cubic (abbreviated ''cI'' or bcc) *Face-centered cubic (abbreviated ''cF'' or fcc, and alternatively called ''cubic close-packed'' or ccp) Each is subdivided into other variants listed below. Although the ''unit cells'' in these crystals are conventionally taken to be cubes, the primitive unit cells often are not. Bravais lattices The three Bravais lattices in the cubic crystal system are: The primitive cubic lattice (cP) consists of one lattice point on each corner of the cube; this means each simple cubic unit cell has in total one lattice point. Each atom at a lattice point is then shared equally between eight adjacent cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequence of database operations that satisfies the ACID properties (which can be perceived as a single logical operation on the data) is called a ''transaction''. For example, a transfer of funds from one bank account to another, even involving multiple changes such as debiting one account and crediting another, is a single transaction. In 1983, Andreas Reuter and Theo Härder coined the acronym ''ACID'', building on earlier work by Jim Gray who named atomicity, consistency, and durability, but not isolation, when characterizing the transaction concept. These four properties are the major guarantees of the transaction paradigm, which has influenced many aspects of development in database systems. According to Gray and Reuter, the IBM Inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reducing Agents
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth metals, formic acid, oxalic acid, and sulfite compounds. In their pre-reaction states, reducers have extra electrons (that is, they are by themselves reduced) and oxidizers lack electrons (that is, they are by themselves oxidized). This is commonly expressed in terms of their oxidation states. An agent's oxidation state describes its degree of loss of electrons, where the higher the oxidation state then the fewer electrons it has. So initially, prior to the reaction, a reducing agent is typically in one of its lower possible oxidation states; its oxidation state increases during the reaction while that of the oxidizer decreases. Thus in a redox reaction, the agent whose oxidation state increases, that "loses/ donates electrons", that "is oxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition Metal Oxides
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(II) Compounds
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardness. A major development in steel production was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating (electroplating with chromium) together comprise 85% of the commercial use. Chromium is also greatly valued as a metal that is able to be highly polished while resisting tarnishing. Polished chromium reflects almost 70% of the visible spectrum, and almost 90% of infrared light. The name of the element is derived from the Greek word χρῶμα, ''chrōma'', meaning color, because many chromium compounds are intensely colored. Industrial production of chromium proceeds from chromite ore (mostly FeCr2O4) to produce ferroc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(VI) Oxide
Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions, bright orange when wet and which dissolves in water concomitant with hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser and a carcinogen. Production, structure, and basic reactions Chromium trioxide is generated by treating sodium dichromate with sulfuric acid: :H2SO4 + Na2Cr2O7 → 2 CrO3 + Na2SO4 + H2O Approximately 100,000 tonnes are produced annually by this or similar routes. The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices. Each chromium center therefore shares two oxygen centers with neighbors. Two oxygen atoms are not shared, giving an overall stoichiometry of 1:3. : The st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(IV) Oxide
Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO2. It is a black synthetic magnetic solid. It once was widely used in magnetic tape emulsion. With the increasing popularity of CDs and DVDs, the use of chromium(IV) oxide has declined. However, it is still used in data tape applications for enterprise-class storage systems. It is still considered by many oxide and tape manufacturers to have been one of the best magnetic recording particulates ever invented. Preparation and basic properties CrO2 was first prepared by Friedrich Wöhler by decomposition of chromyl chloride. Acicular chromium dioxide was first synthesized in 1956 by Norman L. Cox, a chemist at E.I. DuPont, by decomposing chromium trioxide in the presence of water at a temperature of and a pressure of 200 MPa. The balanced equation for the hydrothermal synthesis is: :3 CrO3 + Cr2O3 → 5 CrO2 + O2 The magnetic crystal that forms is a long, slender glass-like rod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphoterism
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used. One type of amphoteric species are amphiprotic molecules, which can either donate or accept a proton (). This is what "amphoteric" means in Brønsted–Lowry acid–base theory. Examples include amino acids and proteins, which have amine () and carboxylic acid () groups, and self-ionizable compounds such as water. Ampholytes are amphoteric molecules that contain both acidic and basic functional groups. For example, an amino acid has both a basic group and an acidic group , and exists as several structures in chemical equilibrium: :H2N-RCH-CO2H + H2O H2N-RCH-COO- + H3O+ H3N+-RCH-COOH + OH- H3N+-RCH-COO- + H2O In approximately neutral aqueous solution (pH ≅ 7), the basic amino group is mostly protonated and the carboxylic acid is mostly deprotonated, so that the predominant sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base (chemistry)
In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century. In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form Hydroxide ions OH−. These ions can react with hydrogen ions (H+ according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction. A base was therefore a metal hydroxide such as NaOH or Ca(OH)2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter and change the color of pH indicators (e.g., turn red litmus paper blue). In water, by altering the autoionization equilibrium, bases yield solutions in which the hydrogen ion activity is lower than it is in pure water, i.e., the water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pearson Symbol
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W. B. Pearson. The symbol is made up of two letters followed by a number. For example: * Diamond structure, ''cF''8 * Rutile structure, ''tP''6 The two (italicised) letters specify the Bravais lattice. The lower-case letter specifies the crystal family, and the upper-case letter the centering type. The number at the end of the Pearson symbol gives the number of the atoms in the conventional unit cell.Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 IR-3.4.4, pp. 49–51; IR-11.5, pp. 241–242. |
Hypophosphorous Acid
Hypophosphorous acid (HPA), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent with molecular formula H3PO2. It is a colorless low-melting compound, which is soluble in water, dioxane and alcohols. The formula for this acid is generally written H3PO2, but a more descriptive presentation is HOP(O)H2, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites. HOP(O)H2 exists in equilibrium with the minor tautomer HP(OH)2. Sometimes the minor tautomer is called hypophosphorous acid and the major tautomer is called phosphinic acid. Preparation and availability Hypophosphorous acid was first prepared in 1816 by the French chemist Pierre Louis Dulong (1785–1838). The acid is prepared industrially via a two step process: Firstly, elemental white phosphorus reacts with alkali and alkaline earth hydroxides to give an aqueous solution of hypophosphites: :P4 + 4 OH− + 4 H2O → 4 + 2 H2 Any phosp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(III) Oxide
Chromium(III) oxide (or chromia) is an inorganic compound with the formula . It is one of the principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite. Structure and properties has the corundum structure, consisting of a hexagonal close packed array of oxide anions with of the octahedral holes occupied by chromium. Similar to corundum, is a hard, brittle material (Mohs hardness 8 to 8.5). It is antiferromagnetic up to 307 K, the Néel temperature. It is not readily attacked by acids. Occurrence occurs naturally as the mineral eskolaite, which is found in chromium-rich tremolite skarns, metaquartzites, and chlorite veins. Eskolaite is also a rare component of chondrite meteorites. The mineral is named after Finnish geologist Pentti Eskola. Production The Parisians Pannetier and Binet first prepared the transparent hydrated form of in 1838 via a secret process, sold as a pigment. It is derived from the mineral chromite, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
