CHEMISTRY GLOSSARY

conditional electrode potential    →   uvjetni elektrodni potencijal

Conditional or formal electrode potential (E°’) is equal to electrode potential (E) when overall concentrations of oxidised and reduced form in all its forms in a solution are equal to one. Conditional electrode potential includes all effects made by reactions that do not take part in the electron exchange, but lead to change of ion power, changes of pH, hydrolysis, complexing, precipitating, etc.

At 298 K (25 °C) and by converting natural (Napierian) logarithms into decimal (common, or Briggian) logarithms, Nernst’s equation for electrode potential can be written as follows:

contact procedure    →   kontaktni postupak

Contact procedure is an industrial procedure used for the production of sulphuric acid, where a dry and clean sulphur dioxide and air go over a catalyst made of vanadium pentoxide at 450 °C by which sulphur trioxide is gained, then we add concentrated sulphuric acid by which we obtain smoking sulphuric acid which is now diluted to sulphuric acid.

diffusion    →   difuzija

Diffusion is the spontaneous mixing of one substance with another when in contact or separated by a permeable membrane. Diffusion is a result of the random motions of their component atoms, molecules, ions, or other particles. Diffusion occurs most readily in gases, less so in liquids, and least in solids. The rate of diffusion is proportional to the concentration of the substance and increases with temperature. The theoretical principles are stated in Fick’s laws.

dissociation constant    →   konstanta disocijacije

Dissociation constant is a constant whose numerical value depends on the equilibrium between the undissociated and dissociated forms of a molecule. A higher value indicates greater dissociation.

The term dissociation is also applied to ionisation reactions of acids and bases in water. For example

which is often regarded as a straightforward dissociation into ions

The equilibrium constant of such a dissociation is called the acid dissociation constant or acidity constant, given by

The concentration of water [H₂O] can be taken as constant.

Similarly, for a base, the equilibrium

is also a dissociation; with the base dissociation constant or basicity constant, given by

K_a (K_b) is a measure of the strength of the acid (base).

fire-damp    →   plin praskavac

Fire-damp is a mixture of two volume parts of hydrogen and one volume part of oxygen which, if set on fire, strongly explodes, the flame giving of a very high temperature (2 000 °C).

fraction    →   udio

Fraction is a ratio of two quantities of the same kind, the numerator quantity applying to one constituent (or part) of the system and the denominator to the sum of quantities for all constituents (parts) of the system. When applied to mixtures fractions represent a group of three quantities: mass fraction, volume fraction and amount fraction (or mole fraction equal to the number fraction).

infrared spectroscopy    →   infracrvena spektroskopija

Infrared (IR) spectroscopy is a technique used for determining the structure (and sometimes concentration) of molecules by observing how infrared radiation is absorbed by a sample.

law of chemical equilibrium    →   zakon o kemijskoj ravnoteži

Law of chemical equilibrium (also called the law of mass action) states that the rate at which a substance reacts is proportional to its active mass (i.e. to its molar concentration). Thus, the velocity of a chemical reaction is proportional to the product of the concentration of the reactants.

distillation    →   destilacija

Distillation is a process of boiling a liquid and condensing and collecting the vapour. The liquid collected is the distillate. The usual purpose of distillation is purification or separation of the components of a mixture. This is possible because the composition of the vapour is usually different from that of liquid mixture from which it is obtained. Petrol, kerosene, fuel oil, and lubricating oil are produced from petroleum by distillation.

electrode of the first kind    →   elektroda prvog reda

Electrode of the first kind is a simple metal electrode immersed in a solution containing its own ion (e.g., silver immersed in a silver nitrate solution). The equilibrium potential of this electrode is a function of the concentration (more correctly of activity) of the cation of the electrode metal in the solution (see Nernst’s electrode potential equation).