CHEMISTRY GLOSSARY

weak base    →   slaba baza

Weak base is a base that only partially dissociates into ions in solution. Weak bases are weak electrolytes. Ammonia is an example of a weak base

basic Bessemer process    →   bazni Bessemerov proces

Basic Bessemer process is the process of steelmaking in a way that steel, melted iron and limestone are put in the blast-furnace after which the metal oxygen is released in gushes in order to oxidise the impurities.

basic liquid    →   matična otopina

Basic liquid is a liquid left after crystallizations.

ABS plastic    →   ABS

ABS plastic is any of a class of plastics or plastics based on acrylonitrile-butadiene-styrene copolymers.

absolute temperature    →   apsolutna temperatura

Absolute temperature denoting a temperature measured on the absolute scale, a scale of temperature based on absolute zero as the lowest temperature.

acid    →   kiselina

Acid is a type of compound that contains hydrogen and dissociates in water to produce positive hydrogen ions. The reaction for an acid HA is commonly written:

In fact, the hydrogen ion (the proton) is solvated, and the complete reaction is:

This definition of acids comes from the Arrhenius theory. Such acids tend to be corrosive substances with a sharp taste, which turn litmus red and produce colour changes with other indicators. They are referred to as protonic acids and are classified into strong acids, which are almost completely dissociated in water, (e.g. sulphuric acid and hydrochloric acid), and weak acids, which are only partially dissociated (e.g. acetic acid and hydrogen sulphide). The strength of an acid depends on the extent to which it dissociates, and is measured by its dissociation constant.

In the Lowry-Brønsted theory of acids and bases (1923), the definition was extended to one in which an acid is a proton donor (a Brønsted acid), and a base is a proton acceptor (a Brønsted base). An important feature of the Lowry-Brønsted concept is that when an acid gives up a proton, a conjugate base is formed that is capable of accepting a proton.

Similarly, every base produces its conjugate acid as a result of accepting a proton.

For example, acetate ion is the conjugate base of acetic acid, and ammonium ion is the conjugate acid of ammonia.

As the acid of a conjugate acid/base pair becomes weaker, its conjugate base becomes stronger and vice versa.

A further extension of the idea of acids and bases was made in the Lewis theory. In this, a G. N. Lewis acid is a compound or atom that can accept a pair of electrons and a Lewis base is one that can donate an electron pair. This definition encompasses "traditional" acid-base reactions, but it also includes reactions that do not involve ions, e.g.

in which NH₃ is the base (donor) and BCl₃ the acid (acceptor).

adenine    →   adenin

Adenine is a purine derivative. It is one of the major component bases of nucleotides and the nucleic acid DNA and RNA.

aerogel    →   aerogel

Aerogel is a low-density porous transparent material that consists of more than 90 % air. Usually based on metal oxides or silica, aerogels are used as drying agents and insulators.

alkaloid    →   alkaloid

Alkaloids are basic nitrogen organic compounds (mostly heterocyclic) derived from plants and having diverse pharmacological properties. Alkaloids include morphine, cocaine, atropine, quinine, and caffeine, most of which are used in medicine as analgesics or anaesthetics. Some alkaloids are poisonous, e.g. strychnine and coniine, and colchicine inhibit cell division.

aluminate    →   aluminat

Aluminate is a salt formed when aluminium hydroxide or y-alumina is dissolved in solutions of strong bases, such as sodium hydroxide. Aluminates exist in solutions containing the aluminate ion, commonly written [Al(OH)₄]^-. In fact the ion probably is a complex hydrated ion and can be regarded as formed from a hydrated Al³⁺ ion by removal of four hydrogen ions:

Other aluminates and polyaluminates, such as [Al(OH)₆]^3- and [(HO)₃AlOAl(OH)₃]^2-, are also present.