CHEMISTRY GLOSSARY

equivalent    →   ekvivalent

Equivalent (eq) is a unit for describing the amount of a chemical species. In contrast to the mole, the amount of a substance contained in one equivalent can vary from reaction to reaction.

equivalence point    →   točka ekvivalencije

Eequivalence point is the point in a titration when enough titrant has been added to react completely with the analyte.

equivalent weight    →   ekvivalentna masa

Equivalent weight of a substance participating in a neutralization reaction is that mass of substance (molecule, ion, or paired ion) that either reacts with or supplies 1 mol of hydrogen ions in that reaction.

Equivalent weight of a substance participating in an oxidation/reduction reaction is that weight which directly or indirectly produces or consumes 1 mol of electrons.

mass-energy equivalence    →   ekvivalencija mase i energije

In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total "mass-energy" was conserved. The relationship between the mass and the energy is contained in what is probably the most famous equation in science,

Where m is the mass of the object and c is the velocity of light. Cockcroft and Walton (1932) are routinely credited with the first experimental verification of mass-energy equivalence.

biocapacity    →   biokapacitet

Biocapacity (or biological capacity) is the capacity of ecosystems to produce useful biological materials and to absorb carbon dioxide generated by humans, using current management schemes and extraction technologies. Useful biological materials are defined as those used by the human economy, hence what is considered useful can change from year to year. The biocapacity of an area is calculated by multiplying the actual physical area by the yield factor and the appropriate equivalence factor.

Yield factor is a factor that accounts for differences between countries in productivity of a given land type. Each country and each year has yield factors for cropland, grazing land, forest, and fisheries.

Equivalence factor is a productivity based scaling factor that converts a specific land type into a universal unit of biologically productive area, a global hectare (gha).

cetane number    →   cetanski broj

Cetane number is a measure of the ignition quality of diesel fuel. It denotes the volume fraction of cetane (C₁₆H₃₄) in a combustible mixture (containing cetane and 1-methylnapthalene) whose ignition characteristics match those of the diesel fuel being tested. Cetane is a collection of un-branched open chain alkane molecule that ignites very easily under compression, so it was assigned a cetane number of 100, while alpha-methyl naphthalene was assigned a cetane number of 0.

chemical equation    →   kemijska jednadžba

Chemical equation is a way of denoting a chemical reaction using the symbol for the participating particles (atoms, molecules, ions, etc.); for example,

The single arrow is used for an irreversible reaction; double arrows are used for reversible reactions. When reactions involve different phases, it is usual to put the phase in brackets after the symbol.

The numbers a, b, c, and d, showing the relative numbers of molecules reacting, are called the stoichiometric coefficients. The convention is that stoichiometric coefficients are positive for reactants and negative for products. If the sum of the coefficients is zero, the equation is balanced.

conductometry    →   konduktometrija

Conductometry is a volumetric analytic method in which the end of titration (equivalent point) is defined by an electric conductivity appliance.

chlorinity    →   klorinitet

Originally chlorinity (symbol Cl) was defined as the weight of chlorine in grams per kilogram of seawater after the bromides and iodides had been replaced by chlorides. To make the definition independent of atomic weights, chlorinity is now defined as 0.3285233 times the weight of silver equivalent to all the halides.

The Mohr-Knudsen titration method served oceanographers for more than 60 years to determine salinity from chlorinity. This modification of the Mohr method uses special volumetric glassware calibrated directly in chlorinity units. The Mohr method uses potassium chromate (K₂CrO₄) as an indicator in the titration of chloride ions chloride (plus a small amount of bromide and iodide) with a silver nitrate (AgNO₃) standard solution.

The other halides present are similarly precipitated.

A problem in the Mohr titration was that silver nitrate is not well suited for a primary standard. The Danish physicist Martin Knudsen (1871-1949) suggested that a standard seawater (Eau de mer Normale or Copenhagen Normal Water) be created and distributed to oceanographic laboratories throughout the world. This water was then used to standardize the silver nitrate solutions. In this way all chlorinity determinations were referred to one and the same standard which gave great internal consistency.

The relationship between chlorinity Cl and salinity S as set forth in Knudsen's tables is

In 1962, however, a better expression for the relationship between total dissolved salts and chlorinity was found to be

Einstein, Albert    →   Einstein, Albert

Albert Einstein (1879-1955) is a German born American physicist, who took Swiss nationality in 1901. A year later he went to work in the Bern patent office. In 1905. he published five enormously influential papers, one on Brownian movement, one on the photoelectric effect, one on the special theory of relativity, and one on energy and inertia (which included the famous expression E = mc²). In 1915 he published the general theory of relativity, concerned mainly with gravitation. In 1921 he was awarded the Nobel Prize. In 1933, as a Jew, Einstein decided to remain in the USA (where he was lecturing), as Hitler had come to power. For the remainder of his life he sought a unified field theory. In 1939 he informed president Roosevelt that an atom bomb was feasible and that. Germany might be able to make one.