CHEMISTRY GLOSSARY

thermosphere    →   termosfera

Thermosphere is the layer of the earth’s atmosphere extending from the top of the mesosphere (80 km - 90 km above the surface) to about 500 km. It is characterised by a rapid increase in temperature with increasing altitude up to about 200 km, followed by a levelling off in the 300 km - 500 km region.

troposphere    →   troposfera

Troposphere is the lowest part of the earth’s atmosphere, extending to 10 km to 15 km above the surface. It is characterized by a decrease in temperature with increasing altitude. The exact height varies with latitude and season.

unsaturated fat    →   nezasićena mast

Unsaturated fats, which include one or more unsaturated fatty acid, are liquid at room temperature (oil) and come from plant oils such as olive, peanut, corn, sunflower, safflower, and soybean. The fish oils may also be high in unsaturated fatty acids.

van der Waals’ equation    →   van der Waalsova jednadžba

Van der Waals’ equation is an equation of state for real fluids which takes the form:

where p is pressure, V_m is molar volume, T is temperature, R is the molar gas constant, and a and b are characteristic parameters of the substance which describe the effect of attractive and repulsive intermolecular forces.

van’t Hoff equation    →   van Hoffova jednadžba

Van’t Hoff equation is the equation expressing the temperature dependence on the equilibrium constant K of a chemical reaction:

where Δ_rH° is the standard enthalpy of reaction, R the molar gas constant, and T the temperature.

vanadium    →   vanadij

Vanadium was discovered by A. M. del Rio (Spain) in 1801 and rediscovered by Nils Sefstrom (Sweden) in 1830. Named after Vanadis, the goddess of beauty in Scandinavian mythology. It is soft, ductile, silvery-white metal. Resistant to corrosion by moisture, air and most acids and alkalis at room temperature. Exposed surfaces form oxide coating. Reacts with concentrated acids. Vanadium is found in the minerals patronite (VS₄), vanadinite [Pb₅(VO₄)₃Cl] and carnotite [K₂(UO₂)₂(VO₄)₂·3H₂O]. Pure metal produced by heating with C and Cl to produce VCl₃ which is heated with Mg in Ar atmosphere. It is mixed with other metals to make very strong and durable alloys. Vanadium pentoxide (V₂O₅) is used as a catalyst, dye and fixer-fixer.

volumetric flask    →   odmjerna tikvica

Volumetric flasks are bottles made of glass, in a pear like in shape with long thin necks and flat bottoms. All come with a ground glass stopper for a tight seal. Volume marking is cut in glass with fluoride acid around the neck, so that parallax should be avoided (flask is put in front of the eyes so that one can see only a straight horizontal line). A volumetric flask is calibrated to contain (TC or In) the indicated volume of water at 20 °C when the bottom of the meniscus is adjusted to just rest on the center of the line marked on the neck of the flask. They are used for preparing the exactly known volume of sample solution and standard solutions of reagents. On each flask with volume designation a temperature on which the flask has been calibrated is designated.

water    →   voda

Water (H₂O) (dihydrogen oxide) is a binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 °C and boils above 100 °C. Water is a chemical compound which is essential for living organisms and it is widely used as a solvent.

water gas    →   vodeni plin

Water gas (blue gas, synthesis gas) is a fuel gas used in industrial synthesis of organic chemicals, and in welding, glassmaking, and other high-temperature industrial applications. Water gas is made by passing steam over a bed of hot coal or coke. It mainly consists of carbon monoxide (CO) and hydrogen (H₂), contaminated with small amounts of CO₂, N₂, CH₄, and O₂.

Ziegler process    →   Zieglerov proces

Ziegler process is an industrial process for the manufacture of high-density polyethene using catalysts of titanium(IV) chloride (TiCl₄) and aluminium alkyls (e.g. triethylaluminium, Al(C₂H₅)₃). The process was introduced in 1953 by the German chemist Karl Ziegler (1898-1973). It allowed the manufacture of polythene at lower temperatures (about 60 °C) and pressures (about 1 atm) than used in the original process.