![]() ![]() The equilibrium constant for this reaction can be specified either as a reaction with dissolved carbon dioxide or as a reaction with carbon dioxide gas (see Carbonic acid for values and details). In solution, exposed to air, the hydroxide ion reacts rapidly with atmospheric carbon dioxide, acting as an acid, to form, initially, the bicarbonate ion. A consequence of this is that concentrated solutions of sodium hydroxide have high viscosity due to the formation of an extended network of hydrogen bonds as in hydrogen fluoride solutions. In aqueous solution the hydroxide ion forms strong hydrogen bonds with water molecules. This compound is centrosymmetric and has a very short hydrogen bond (114.5 pm) that is similar to the length in the bifluoride ion HF −Ģ (114 pm). Indeed, the bihydroxide ion HĢ has been characterized in the solid state. In aqueous solution both hydrogen and hydroxide ions are strongly solvated, with hydrogen bonds between oxygen and hydrogen atoms. It can also act as a Lewis base by donating a pair of electrons to a Lewis acid. In aqueous solution the hydroxide ion is a base in the Brønsted–Lowry sense as it can accept a proton from a Brønsted–Lowry acid to form a water molecule. Schematic representation of the bihydroxide ion pOH can be kept at a nearly constant value with various buffer solutions. For example, ammonia solutions have a pH greater than 7 due to the reaction NH 3 + H + ⇌ NH +Ĥ, which decreases the hydrogen cation concentration, which increases the hydroxide ion concentration. Addition of a base to water will reduce the hydrogen cation concentration and therefore increase the hydroxide ion concentration (increase pH, decrease pOH) even if the base does not itself contain hydroxide. ![]() The concentration of hydroxide ions can be expressed in terms of pOH, which is close to (14 − pH), so the pOH of pure water is also close to 7. The pH of a solution is equal to the decimal cologarithm of the hydrogen cation concentration the pH of pure water is close to 7 at ambient temperatures. Has a value close to 10 −14 at 25 ☌, so the concentration of hydroxide ions in pure water is close to 10 −7 mol∙dm −3, in order to satisfy the equal charge constraint. The equilibrium constant for this reaction, defined as The hydroxide ion is natural produced from water by the self-ionization reaction: H 3O + + OH − ⇌ 2H 2O Many inorganic substances which bear the word hydroxide in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups. The corresponding covalently bound group –OH of atoms is the hydroxy group.īoth the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry. The corresponding electrically neutral compound HO Sodium hydroxide is a multi-million-ton per annum commodity chemical. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. It functions as a base, a ligand, a nucleophile, and a catalyst. It is an important but usually minor constituent of water. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. Send us feedback about these examples.Hydroxide is a diatomic anion with chemical formula OH −. These examples are programmatically compiled from various online sources to illustrate current usage of the word 'diatomic.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. 2019 Pairs of oxygen atoms rapidly combine to form the stable diatomic oxygen, which exits with carbon monoxide. Mara Johnson-Groh, Discover Magazine, 2 Dec. 2023 Recently, scientists reported evidence of water vapor, adding to the list that includes cyanide, hydroxide, diatomic carbon and atomic oxygen. 2023 The comet’s green color is caused by diatomic carbon (C2), but more detail can also be worked out. ![]() ![]() 2023 The comet has a bright green glow around its nucleus, due to the effect of sunlight on its molecules, especially diatomic carbon and cyanogen. Recent Examples on the Web For example, think of a pendulum, which is a mass swinging from a string, or the vibrations of a diatomic molecule (a molecule with two atoms, like nitrogen), or even the change in electric current in something like a circuit inside a radio that makes an oscillation. ![]()
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