hidroksid

Hidroksid is the Swedish term for the chemical compound hydroxide, which consists of a metal or nonmetal cation bonded to the hydroxide anion (OH−). Hydroxides are basic salts and are generally represented by the formula M(OH)n, where M is the cationic species and n is its valency. They can be prepared by reacting a metal oxide or metal hydroxide with water, or by neutralisation of an acid with a base.

The hydroxide anion has a lone pair of electrons that can act as a Lewis base, forming hydrogen bonds and facilitating nucleophilic substitution reactions. In aqueous solutions, hydroxides dissociate to give metal cations and hydroxide ions, raising the pH and making the solution strongly basic. When a hydroxide solution comes into contact with an acid, a double displacement reaction takes place, producing a salt and water.

Common examples of metal hydroxides include calcium hydroxide Ca(OH)2, sodium hydroxide NaOH, and aluminium hydroxide Al(OH)3. They differ in solubility: NaOH and KOH are highly soluble and form caustic solutions, whereas Ca(OH)2 is sparingly soluble and is used in concrete to increase pH. Heavy metal hydroxides such as Fe(OH)3 are insoluble and precipitate as brown solids.

Hydroxides have wide industrial and laboratory uses. NaOH and KOH are used in soap making, detergents, and as strong bases in chemical synthesis. Ca(OH)2 is employed as a cement stabiliser and in flue gas desulphurisation. Certain hydroxides such as aluminium and zinc hydroxides are used as flocculants in water treatment. Biologically, hydroxides of essential trace elements play a role in enzyme function and mineralisation processes.