The hydroxides they are combinations between metal cations and hydroxyl anions (OH–). They are ternary inorganic compounds, since they contain hydrogen, oxygen and a metallic element in their structure. These components are obtained when a metal oxide and water react. For example: sodium hydroxide, barium hydroxide, aluminum hydroxide.
When dissolved in water, the hydroxides dissociate and release the hydroxyl group, in addition to the metal cation. Hydroxides have a strong basic character, this is because the hydroxyl group can capture protons, that is why they are also called bases.
Because of his basic character, hydroxides cause litmus paper (used in chemistry to measure hydrogen ions in a substance) to change from red to blue, and in the presence of phenolphthalein the solution changes from colorless to pink. Hydroxides react with acids to produce a salt and water; these reactions generally release energy.
Nomenclature of hydroxides
According to Stock nomenclatureTo name a hydroxide, it is enough to add to the expression “hydroxide of” the name of the metal that composes it. However, some of the metals that can go into combination with hydroxyl groups can assume more than one oxidation state, for example +2 or +3. In this case, it is necessary to indicate in parentheses, after the name of the metal, the oxidation number What does metal work with in Roman numerals?
Another option is to use a suffix in the name of the metal that gives an account of its oxidation state in the molecule (this is known as functional nomenclature). The “bear” ending is the one that corresponds to the lowest oxidation or valence state (of the two that the metal has) and the “ico” ending is the one that corresponds to the highest.
To write the hydroxide formula It must be remembered that the number of hydroxyl will be indicated as a subscript and this will coincide with the oxidation number assumed by the metal.
Examples of hydroxides
- Sodium hydroxide, NaOH. Better known as caustic soda, this hydroxide is used to make crayons, soaps, dyes, explosives, petroleum products, and paper. It is also used in different types of cleaners, detergents and to unclog pipes. Sodium hydroxide is also used in the textile industry, in the production of various medicines, in food processing and in water treatment.
- Barium hydroxide, Ba (OH)two. It is used in the manufacture of ceramics and different types of poisons. In addition, it is used as an additive in plastics and lubricants.
- Aluminum hydroxide, Al (OH)3. It is used in medicine to make drugs to relieve various stomach upsets and as a phosphate chelator (used to reduce phosphate absorption). It is also used as a raw material for the manufacture of other compounds.
- Zinc hydroxide, Zn (OH)two. It is used as an adsorbent; Nanoparticles of this hydroxide have also been formulated.
- Ferric hydroxide, Fe (OH)3. It is used in the absorption of polluting substances in media such as water. In addition, it is used in the manufacture of paints, cosmetics and medicines (which combat the lack of iron in the body).
- Ferrous hydroxide, Fe (OH) 2. It is widely used in the metallurgical industry.
- Cupric hydroxide, Cu (OH)two. It is used as a laboratory reagent and also as a fungicide and biocide. In addition, it is used in the manufacture of rayon, as a pigment and as a colorant for ceramics.
- Cuprous hydroxide, CuOH. Similar to cupric hydroxide (Cu (OH)two), it is used as a fungicide and colorant.
- Calcium hydroxide, Ca (OH)two. It is the so-called dead lime or slaked lime, which is used in construction. It is also used in water treatment, as a fertilizer, in the chemical and metallurgical industry, and in food production (such as dairy and salt). In addition, it is a widely used material in the field of dentistry.
- Lithium hydroxide, LiOH. It is used to remove carbon dioxide in purification systems and in lubricating batteries and greases.
- Chromium (III) hydroxide, Cr (OH)3. It is used in the manufacture of paints, especially to achieve green pigments, and as a mordant. In addition, it is used as a colorant in textiles, cosmetics and food.
- Lead (IV) hydroxide, Pb (OH)4. It is mainly used in cable covers, electrical insulation paper and some types of batteries.
- Gold (III) hydroxide, Au (OH)3. It is used in many fields of medicine and also to decorate porcelain, ceramics and make gold-plated.
- Silver hydroxide, AgOH. It is used in products that work to detect chloride in other solutions.
- Mercuric hydroxide, Hg (OH)two. Due to its high level of toxicity, it is not used in everyday items.
- Beryllium hydroxide, Be (OH)two. It is used as a raw material in obtaining metallic beryllium and is not usually used for everyday items.
- Lead (II) hydroxide, Pb (OH)two. It is often used for coatings.
- Platinum (IV) hydroxide, Pt (OH)4. It is used for the production of extremely fine wires.
- Cobalt (II) hydroxide, Co (OH)two. It is used in the preparation of cobalt salts. In addition, it is used in the oil industry, to manufacture battery electrodes and for drying paints.
- Manganese (III) hydroxide, Mn (OH)3. It forms different types of green crystals and is not widely used for the manufacture of goods or products.
- Strontium hydroxide, Sr (OH)two. It is used in the manufacture of lubricating grease and in the plastics manufacturing process in which it is used as a stabilizer.
- Magnesium hydroxide, Mg (OH)two. It is also known as milk of magnesium and is used primarily as an antacid or laxative.
- Tin (II) hydroxide, Sn (OH)two. It is used in the dyes of the fabric industry.
- Ammonium hydroxide, NH4Oh. It is used in cleaning products, fertilizers and in refrigeration equipment. It is also used in food processing.
- Cadmium hydroxide, Cd (OH)two. It is used in the manufacture of industrial accumulator batteries and enamels.