CHEMISTRY GLOSSARY

electrode of the third kind    →   elektroda trećeg reda

Electrode of the third kind is a metal electrode assembly with the equilibrium potential being a function of the concentration of a cation, other than the cation of the electrode metal, in the solution. The assembly consists of a metal in contact with two slightly soluble salts (one containing the cation of the solid metal, the other the cation to be determined, with both salts having a common anion) immersed in a solution containing a salt of the second metal (e.g., zinc metal--zinc oxalate--calcium oxalate--calcium salt solution). The potential of the metal is controlled by the concentration of its cation in the solution, but this is controlled by the anion concentration in the solution through the solubility product of the slightly soluble metal salt, which, in turn is controlled by the concentration of the cation of the second slightly soluble salt. These electrodes are very sluggish and unstable due to a series of equilibria to be established to produce a stable potential.

electrodeposition    →   elektrodepozicija

Electrodeposition is a process of depositing solid materials on an electrode surface using electrolysis. It is a somewhat loosely used term that is applied to many technologies. There are a number of metal deposition technologies. However, not only metals but also different compounds can be electrodeposited. This is used most often for the formation of oxides (such as manganese dioxide and lead dioxide) by anodic oxidation of dissolved salts.

electrodialysis    →   elektrodijaliza

Electrodialysis is a procedure of dialysis accelerated with an electric field. Dialyser is divided into three sections. Solution flows through the middle section, between two semipermeable membranes alternately to positive ions and negative ions. An electrodes are placed in the neighbouring sections. Under the influence of electric field, positive ions will travel towards the cathode (the negative electrode), and negative ions towards the anode (the positive electrode), whereby travelling of ions through the membrane is accelerated. In this way, the feed water is separated into two streams: one of pure water and the other of more concentrated solution.

harmonic oscillation    →   harmonička oscilacija

Harmonic is an oscillation having a frequency is a simple multiple of a fundamental sinusoidal oscillation. The fundamental frequency of a sinusoidal oscillation is usually called the first harmonic. The second harmonic has a frequency twice that of the fundamental, and so on.

heat    →   toplina

Heat is a form of energy associated with and proportional to molecular motion. It can be transferred from one body to another by radiation, conduction, or convection.

Heat of atomisation    →   toplina atomiziranja

Heat of atomisation or enthalpy of atomisation is the energy required to dissociate one mole of a given substance into atoms.

electrode potential    →   elektrodni potencijal

Electrode potential is defined as the potential of a cell consisting of the electrode in question acting as a cathode and the standard hydrogen electrode acting as an anode. Reduction always takes place at the cathode, and oxidation at the anode. According to the IUPAC convention, the term electrode potential is reserved exclusively to describe half-reactions written as reductions. The sign of the half-cell in question determines the sign of an electrode potential when it is coupled to a standard hydrogen electrode.

Electrode potential is defined by measuring the potential relative to a standard hydrogen half cell

The convention is to designate the cell so that the oxidised form is written first. For example

The e.m.f. of this cell is

By convention, at p(H₂) = 101325 Pa and a(H⁺) = 1.00, the potential of the standard hydrogen electrode is 0.000 V at all temperatures. As a consequence of this definition, any potential developed in a galvanic cell consisting of a standard hydrogen electrode and some other electrode is attributed entirely to the other electrode

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.

heat of crystallization    →   toplina kristalizacije

Heat of crystallization or enthalpy of crystallization is the heat evolved or absorbed when one mole of given substance crystallises from a saturated solution of the same substance.

heat of formation    →   toplina nastajanja

Heat of formation or enthalpy of is formation the heat evolved or absorbed when one mole of a compound is formed in its standard state from its constituent elements.