hydroxides

Hydroxides are inorganic compounds that contain the hydroxide anion OH−. They typically form salts or bases when combined with metal ions.

The hydroxide ion has one oxygen and one hydrogen, with a negative charge; in solid hydroxides the ions form ionic lattices with metal cations. Solubility varies: alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are highly soluble in water, while many alkaline earth hydroxides are only moderately or sparingly soluble.

Preparation and reactions: Most hydroxides are prepared by reacting water with metal oxides (for example CaO + H2O → Ca(OH)2). In aqueous solution they function as bases, accepting protons; they neutralize acids to form water and a salt (NaOH + HCl → NaCl + H2O). Alkaline earth hydroxides are less soluble but still basic.

Occurrence and uses: Some hydroxides occur naturally as minerals (brucite Mg(OH)2, gibbsite Al(OH)3, portlandite Ca(OH)2). Industrially, NaOH and KOH are used in chemical manufacturing, Ca(OH)2 in cement and refining, Mg(OH)2 as an antacid and stabilizer, and Al(OH)3 in fire retardants and decolorizers. In water treatment, hydroxides can raise pH and precipitate metals.

Safety: Many hydroxides are caustic; handling requires proper protection. Hydroxide solutions are corrosive and can cause burns.