Hydroxides are combinations of metal cations and anions hydroxyl (OH – ) . It is, therefore, ternary inorganic compounds , since they contain hydrogen, oxygen and a metallic element in their molecule.
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, so they are also called bases.
Characteristics of hydroxides
According to the Stock nomenclature , to name a hydroxide, it is enough to add to the expression “hydroxide of” the name of the metal that composes it. But it happens that some of the metals that can enter in combination with hydroxyl groups can assume more than one oxidation state, for example, +2 or +3.
In this case the nomenclature is complicated and it is necessary to indicate in parentheses , following the name of the metal, the oxidation number with which the metal acts in Roman numerals .
Another option is to resort to a suffix in the name of the metal that accounts for the oxidation state of that in the molecule ; This is known as functional nomenclature. The “bear” termination is the one that corresponds to the lowest oxidation or valence state (of the two that the metal has), the “ico” termination corresponds to the major.
To write the molecular formula , remember that the number of hydroxyls will be indicated as a subscript and this will coincide with the number of oxidation assumed by the metal.
Due to their basic character, hydroxides cause the litmus paper to change color from red to blue , and in the presence of phenolphthalein the solution turns colorless to red. Hydroxides react with acids to produce a salt and water; Generally these reactions release energy.
The uses of hydroxides
Hydroxides have different uses in everyday life. For example, soda or caustic potash (sodium and potassium hydroxide, respectively) are used to unclog pipes.
Magnesium hydroxide is well known as antacid, many stomach digestives include it in its formulation. At higher concentrations it has laxative power.
Aluminum hydroxide is also used as an antacid in so-called fruit salts. Calcium hydroxide is widely used in construction, it is known in that area as slaked lime .
Examples of hydroxides
Twenty- five hydroxides are listed below , and their uses
- Sodium hydroxide , NaOH : Used in the textile industry, it is also used to make crayons and paper. Also used in different types of cleaners, such as paint.
- Barium hydroxide , Ba (OH) 2 : Used in the manufacture of ceramics and different types of poisons.
- Aluminum hydroxide , Al (OH) 3 : Typically used to relieve different stomach discomforts.
- Zinc hydroxide , Zn (OH) 2 : It is used as an adsorbent; nanoparticles of this hydroxide have also been formulated.
- Ferric hydroxide , Fe (OH) 3 : It is used in the manufacture of paints and medicines.
- Ferrous hydroxide , Fe (OH) 2 : Very important in the metallurgical industry.
- Cupric hydroxide , Cu (OH) 2 : Laboratory reagent, also used as a fungicide.
- Cuprous hydroxide , CuOH : Similar to cupric hydroxide
- Calcium hydroxide , Ca (OH) 2 : It is the so-called dead lime or slaked lime, so important in construction. It is also used in agriculture and in the chemical, pharmaceutical and food industry.
- Lithium hydroxide , LiOH : Used to remove carbon dioxide in purification systems.
- Chromium hydroxide (III), Cr (OH) 3 : Used to make paints, especially to achieve green colors.
- Lead (IV) hydroxide , Pb (OH) 4 : Mainly used in cable covers.
- Gold hydroxide (III), Au (OH) 3 : Used in many fields of medicine and ceramics.
- Silver hydroxide , AgOH: It is used to form certain products that work to detect chloride in other solutions.
- Mercuric hydroxide , Hg (OH) 2 : Used less and less for its toxicity.
- Beryllium hydroxide , Be (OH) 2 : It can form a positive ion as well as a negative one.
- Lead (II) hydroxide , Pb (OH) 2 : Typically used for coatings.
- Platinum (IV) hydroxide , Pt (OH) 4 : Used for the elaboration of extremely fine wires.
- Cobalt hydroxide , Co (OH) 2 : Used in the preparation of cobalt salts.
- Manganese hydroxide , Mn (OH) 3 : It forms different types of green crystals.
- Strontium hydroxide , Sr (OH) 2 : Absorbs carbon dioxide from the air.
- Magnesium hydroxide , Mg (OH) 2 : Used as an antacid or laxative.
- Tin hydroxide (II), Sn (OH) 2: Common in the dyes of the fabric industry.
- Ammonium hydroxide , NH 4 OH: Mainly used in food processing.
- Cadmium hydroxide , Cd (OH) 2 : Found in batteries of industrial accumulators.