Lesson declared

Hydroxide and oxide

• After finished this lesson student will to able to

• # Say about the Hydroxide • # Say about Hydroxide ion.• # Say about Oxide.

Hydroxide

• Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution,

• liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. A hydroxide attached to a strongly electropositive center may itself ionize, liberating a hydrogen cation (H+), making the parent compound an acid.

• The corresponding electrically neutral compound •HO is the hydroxyl radical. The

• corresponding covalently-bound group -OH of atoms is the hydroxyl group. Hydroxide ion and hydroxyl group are nucleophiles and can act as a catalyst in organic chemistry.

• Many inorganic substances which bear the word "hydroxide" in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxyl groups

• Oxidation states can be useful for balancing chemical equations for oxidation-reduction (or redox) reactions, because the changes in the oxidized atoms have to be balanced by the changes in the reduced atoms. For example, in the reaction of acetaldehyde with the Tollens' reagent to acetic acid (shown below), the carbonyl carbon atom changes its oxidation state from +1 to +3

Hydroxide ion

• The hydroxide ion is a natural part of water, because of the self-ionization reaction:

• H+ + OH− H2O

• The equilibrium constant for this reaction, defined as

• Kw = [H+][OH−] has a value close to 10−14 at 25 °C, 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 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. The concentration of hydroxide ions can be expressed in terms of pOH, which is close to x

• the decimal cologarithm of the hydrogen cation concentration; the pH of pure water is close to 7 at ambient temperatures. The concentration of hydroxide ions can be expressed in terms of pOH, which is close to 14 − pH, so pOH of pure water is also close to 7. 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. For example, ammonia solutions have a pH greater than 7 due to the reaction NH3 + H+ NH4

+, which results in a decrease in hydrogen cation concentration and an increase in hydroxide ion concentration. pOH can be kept at a nearly constant value with various buffer solutions

http://en.wikipedia.org/wiki/File:Bihydoxide.png

Oxide

• Silicon dioxide (SiO2) is one of the most common oxides on the surface of earth. Like most oxides, it adopts a polymeric structure.

• An oxide ɒksaɪd is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide. 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. Different oxides of the same element are distinguished by Roman numerals denoting their oxidation number, e.g. iron(II) oxide versus iron(III) oxide. The two most common oxides in nature are silicon dioxide and water.

Structure

• Oxides of most metals adopt polymeric structures. The oxide typically links three metals (e.g., rutile structure) or six metals (carborundum or rock salt structures) Because the M-O bonds are strong, the solids tend to be insoluble in solvents, though they are attacked by acids and bases. The formulas are often deceptively simple. Many are nonstoichiometric compounds.

Continue,,,,,

• The unit cell of rutile. Ti(IV) centers are grey; oxide centers are red. Notice that oxide forms three bonds to titanium and titanium forms six bonds to oxide.

• # Explain Hydroxide

• # Explain Hydroxide ion.

• # What isOxide.