CHEMISTRY GLOSSARY

activity coefficient    →   koeficijent aktiviteta

Activity coefficient (γ or f) is a fractional number which, when multiplied by the molar concentration of a substance in solution, yields the chemical activity. This term gives an idea of how much interaction exists between molecules at higher concentration.

In solutions of very low ionic strength, when m is less than 0.01, the Debye-Hückel limiting law can be used to calculate approximate activity coefficients

where γ_i = activity coefficient of the species i, z_i = charge on the species i and μ = ionic strength of the solution.

alkaline earth metal    →   zemnoalkalijski metal

Alkali earth metal is a term that refers to six elements: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements make up group 2 of the periodic table of elements. They all exhibit a single oxidation state, +2. They are all light and very reactive. Barium and radium are the most reactive and beryllium is the least.

To denote slightly soluble metal oxides chemists formerly used the term "earth". The oxides of barium, strontium, and calcium resemble alumina (Al₂O₃), a typical "earth", but form alkaline mixtures with water. For this reason barium, strontium, and calcium were called alkaline earth metals. This name has now been extended to include all of the elements of group 2.

alloy    →   legura

Alloys are solid solutions of metal or nonmetal in metal and are prepared in order to obtain certain properties. In this way alloys can have greater hardness, corrosion resistance or some other properties gained from the metal they are composed.

amperometry    →   amperometrija

Amperometry is determining the concentration of a material in a sample by measuring electric current passing through a cell containing the solution.

anion exchange    →   anionski izmjenjivač

An anionic resin has negative ions built into its structure and therefore exchanges positive ions. In an anion exchange, the side groups are ionised basic groups, such as (-NH₂, -NRH, -NR₂, -NR₃⁺) to which anions OH^- are attached. The exchange reaction is one in which different anions in the solution displace the OH^- from the solid.

battery acid    →   baterijska kiselina

Battery acid is a solution of approximately 6 mol L^-1 sulphuric acid used in the lead storage battery

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.

amount concentration    →   količinska koncentracija

Amount concentration (also called molar concentration and in older literature molarity) is the amount of a given substance in a stated unit of a mixture, solution, or ore. The common unit is mole per cubic decimetre (moldm⁻³) or mole per litre (molL^-1) sometimes denoted by M.

The concentration of an atom, ion, or molecule in a solution may be symbolised by the use of square brackets, as [Ca²⁺].

amount fraction    →   količinski udio

Amount fraction, x_A, (y for gaseous mixtures) is the ratio of the amount of substance (number of moles) of substance A to the total amount of substance in a mixture.

aspartic acid    →   asparaginska kiselina

Aspartic acid is an electrically charged amino acids with acidic side chains. As a group the charged amino acids are relatively abundant and are generally located on the surface of the protein. Aspartic acid and glutamic acid play important roles as general acids in enzyme active centers, as well as in maintaining the solubility and ionic character of proteins. Aspartic acid (sometimes referred to as asparate depending on pH) is non-essential in mammals, being produced from oxaloacetate by transamination.

• Abbreviations: Asp, D
• IUPAC name: 2-aminobutanedioic acid
• Molecular formula: C₄H₇NO₄
• Molecular weight: 133.10 g/mol