CHEMISTRY GLOSSARY

dipole moment    →   dipolni moment

Electric dipole moment (μ) is a product of the positive charge and the distance between the charges. Dipole moments are often stated in debyes; The SI unit is the coulomb metre. In a diatomic molecule, such as HCl, the dipole moment is a measure of the polar nature of the bond; i.e. the extent to which the average electron charges are displaced towards one atom (in the case of HCl, the electrons are attracted towards the more electronegative chlorine atom). In a polyatomic molecule, the dipole moment is the vector sum of the dipole moments of the individual bonds. In a symmetrical molecule, such as tetrafluoromethane (CF₄) there is no overall dipole moment, although the individual C-F bonds are polar.

dissociation    →   disocijacija

Dissociation is the process by which a chemical combination breaks up into simpler constituents as a result of either added energy (dissociated by heat), or the effect of a solvent on a dissolved polar compound (electrolytic dissociation). It may occur in the gaseous, solid, or liquid state, or in a solution.

An example of dissociation is the reversible reaction of hydrogen iodide at high temperatures

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

meson    →   mezon

Meson is a positively or negatively charged subatomic particle of very short life age with a mass about 200 times greater than the one of electron. It is produced artificially in particle accelerators.

metalloid    →   polumetal

Metalloid (semimetal) is any of a class of chemical elements intermediate in properties between metals and nonmetals. The classification is not clear cut, but typical metalloids are boron (B), silicon (Si), germanium (Ge), arsenic (As), and tellurium (Te). They are electrical semiconductors and their oxides are amphoteric.

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).

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

dropper    →   kapaljka

Dropper is a pipette consisting of a small tube with a vacuum bulb at one end for drawing liquid in and releasing it a drop at a time.

millimetre of mercury    →   milimetar živina stupca

Millimetre of mercury (mmHg) is a non-SI unit of pressure, equal to 133.322 Pa. The name is generally considered interchangeable with torr.

Millon’s reaction    →   Millonova reakcija

Millon’s reaction is used for testing proteins by the appearance of red colour which the proteins give by reacting with a solution of mercury in nitric acid.

mineral water    →   mineralna voda

Mineral water is a groundwater that rises to the surface through a natural opening in the earth or rock and contains a relatively high concentration of mineral ions and trace of elements which can be radioactive or thermal.