CHEMISTRY GLOSSARY

distilled water    →   destilirana voda

Distilled water is water purified by distillation so as to free it from dissolved salts and other compounds. Distilled water in equilibrium with the carbon dioxide in the air has conductivity of about 0.8×10^-6 S cm^-1. Repeated distillation in vacuum can bring conductivity down to 0.043×10^-6 S cm^-1 at 18 °C. The limiting conductivity is due to self ionisation

electric cell    →   električni članak

Electric cell (battery) is a device that is capable of changing some form of energy, such as chemical, nuclear or radiant energy, into electricity. A solar cell, for example, consists of a semiconductor junction that converts sunlight directly into electricity. A dry cell battery converts chemical energy into electricity.

electrochemical cell    →   elektrokemijski članak

Electrochemical cell is a device that converts chemical energy into electrical energy or vice versa when a chemical reaction is occurring in the cell. It consist of two electronically conducting phases (e.g., solid or liquid metals, semiconductors, etc) connected by an ionically conducting phase (e.g. aqueous or non-aqueous solution, molten salt, ionically conducting solid). As an electric current passes, it must change from electronic current to ionic current and back to electronic current. These changes of conduction mode are always accompanied by oxidation/reduction reactions.

An essential feature of the electrochemical cell is that the simultaneously occurring oxidation-reduction reactions are spatially separated. E.g., in a spontaneous chemical reaction during the oxidation of hydrogen by oxygen to water, electrons are passed directly from the hydrogen to the oxygen.

In contrast, in the spontaneous electrochemical reaction in a galvanic cell the hydrogen is oxidised at the anode by transferring electrons to the anode and the oxygen is reduced at the cathode by accepting electrons from the cathode. The ions produced in the electrode reactions, in this case positive hydrogen ions and the negative hydroxyl (OH^-) ions, will recombine in the solution to form the final product of the reaction: water. During this process the electrons are conducted from the anode to the cathode through an outside electric circuit where the electric current can drive a motor, light a light bulb, etc. The reaction can also be reversed: water can be decomposed into hydrogen and oxygen by the application of electrical power in an electrolytic cell.

magnetochemistry    →   magnetokemija

Magnetochemistry is a branch of physical chemistry which studies relations between magnetism and the chemical structure of matter.

metabolism    →   metabolizam

Metabolism is a sum of all chemical and physiological processes by which the body builds and maintains itself. It is a process of building the body’s molecular structures from nutrients (anabolism) and breaking them down for energy (catabolism).

microchemistry    →   mikrokemija

Microchemistry is a branch of chemistry that concerns isolating, identifying and an analysis of very small quantities of sample (few mg). It uses delicate reactions, special equipment and microscopes.

electrochemical series    →   elektrokemijski niz

Electrochemical series is a series of chemical elements arranged in order of their standard electrode potentials. The hydrogen electrode

is taken as having zero electrode potential. An electrode potential is, by definition, a reduction potential.

Elements that have a greater tendency than hydrogen to lose electrons to their solution are taken as electropositive; those that gain electrons from their solution are below hydrogen in the series and are called electronegative.

The series shows the order in which metals replace one another from their salts; electropositive metals will replace hydrogen from acids.

electrogravimetry    →   electrogravimetrija

Electrogravimetry is an electroanalytical technique in which the substance to be determined (usually a metal) is deposited out on an electrode which is weighed before and after the experiment. The potential of the electrode must be carefully chosen to ensure that only the metal do be determined will deposit.

electrolytic cell    →   elektrolitska ćelija

Electrolytic cell is an electrochemical cell that converts electrical energy into chemical energy. The chemical reactions do not occur spontaneously at the electrodes when they are connected through an external circuit. The reaction must be forced by applying an external electric current. It is used to store electrical energy in chemical form (rechargeable battery). It is also used to decompose or produce (synthesise) new chemicals by the application of electrical power. This process is called electrolysis, e.g., water can be decomposed into hydrogen gas and oxygen gas. The free energy change of the overall cell reaction is positive.

electronegativity    →   elektronegativnost

Electronegativity is a parameter originally introduced by L. Pauling which describes, on a relative basis, the power of an atom to attract electrons. For example, in hydrogen chloride, the chlorine atom is more electronegative than the hydrogen and the molecule is polar, with a negative charge on the chlorine atom.

There are various ways of assigning values for the electronegativity of an element. Pauling electronegativities are based on bond dissociation energies using a scale in which fluorine, the most electronegative element, has the value 4 and francium, the lowest electronegative element, has the value 0.7.