CHEMISTRY GLOSSARY

battery    →   baterija

Battery a device that converts chemical energy to electrical energy. The process underlying the operation of a battery involves a chemical reaction in which electrons are transferred from one chemical species to another. This process is carried out in two half-reactions, one that involves the loss of electrons and one that involves their gain. The battery is an electrochemical cell divided in two half-cells, and reaction proceeds when these are connected together by an electrically conducting pathway. The passage of electrons from one half-cell to the other corresponds to an electric current. Each half-cell contains an electrode in contact with the reacting species. The electrode which passes electrons into the circuit when battery discharges is called anode and is negative terminal. The electrode which receives electrons is called cathode, and is the battery’s positive terminal. The electrical circuit is completed by an electrolyte, an electrically conducting substance placed between the two electrodes which carriers a flow of charge between them. In wet cells, the electrolyte is a liquid containing dissolved ions, whose motion generates an electrical current; in dry cells the electrolyte is basely solid, for example, a solid with mobile ions or porous solid saturated with an ionic solution.

chemisorption    →   kemisorpcija

Chemisorption is a binding of a liquid or gas on the surface or in the interior of a solid by chemical bonds or forces.

concentrated solution    →   koncentrirana otopina

Concentrated solution is a solution that contains a large amount of solute relative to the amount that could dissolve.

cryoscopic constant    →   krioskopska konstanta

Cryoscopic constant (E_f) is the constant that expresses the amount by which the freezing point T_f of a solvent is lowered by a non-dissociating solute, through the relation

where m is the molality of the solute.

composition of ocean water    →   sastav oceanske vode

The proportions of the major constituents of ocean water are almost constant throughout the world. Salinity (total salt content) and the concentrations of individual chemical constituents in sea wateris given the units psu (practical salinity units). For most purposes one can assume that the new unit, psu, and the older unit, ‰, are synonymous.

The average composition of the ocean water is as shown on the following table.

crystallisation    →   kristalizacija

Crystallisation is process in which the melted substance from a saturated solution turns into solid substance (crystal).

depression of freezing point    →   snižavanje ledišta

Depression of freezing point of a pure solvent is observed when substances are dissolved in it. The amount by which the freezing point is depressed is proportional to the number of molecules of solute and independent of their nature.

dilute solution    →   razrijeđena otopina

Dilute solution contains a relatively low concentration of solute.

ebullioscopic constant    →   ebulioskopska konstanta

Ebullioscopic constant (E_b) is the constant that expresses the amount by which the boiling point T_b of a solvent is raised by a nondissociating solute, through the relation

where b is the molality of the solute.

dialysis    →   dijaliza

Dialysis is a method by which large molecules (such as starch or protein) and small molecules (such as glucose or amino acids) may be separated in a solution by selective diffusion through a semipermeable membrane. Through this kind of membrane dissolved particles pass and colloid dimension particles fall behind. For example, if a mixed solution of starch and glucose is placed in a closed container made of a semipermeable substance (such as cellophane), which is then immersed in a beaker of water, the smaller glucose molecules will pass trough the membrane into the water, while the starch molecules remain behind.