CHEMISTRY GLOSSARY

chemical equation equalization    →   izjednačavanje kemijske jednadžbe

Chemical equation equalization is determining values of stechiometric coefficients of reactants and products in a chemical equation in a way that the number of atoms of each element is equal before and after the reaction.

chemical reaction    →   kemijska reakcija

Chemical reaction is a change of chemical properties of substances which react with each other. By means of a chemical reaction new substances are created by bond breaking between atoms and molecules of reactants and their reuniting in a new way, thereby creating products. Chemical reactions can be shown by chemical equations.

endothermic reaction    →   endotermna reakcija

Endothermic reactions are the ones in which heat is absorbed and are facilitated by an increase in temperature (ΔH° > 0).

If the reaction is endothermal in one direction, in the opposite direction the reaction is exothermal.

catalyst    →   katalizator

Catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Catalysts that have the same phase as the reactants are homogenous catalysts (e.g. enzymes in biochemical reactions). Those that have a different phase are heterogeneous catalyst (e.g. metals or oxides used in gas reactions).

The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. In thus increases the rate at which the reaction comes to an equilibrium, although it does not alter the position of the equilibrium.

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.

forward reaction    →   napredna reakcija

Forward reaction is a reaction in which products are produced from reactants and it goes from left to right in a reversible reaction.

homogenic reaction    →   homogena reakcija

Homogenic reactions are those reactions in which products and reactants are in the same phase (aggregate state).

intermediate    →   intermedijer

Intermediate is a molecular or ionic species that is formed (directly or indirectly) from the reactants and reacts further (directly or indirectly) to form the products of the reaction. It does not accumulate during the course of the reaction.

law of chemical equilibrium    →   zakon o kemijskoj ravnoteži

Law of chemical equilibrium (also called the law of mass action) states that the rate at which a substance reacts is proportional to its active mass (i.e. to its molar concentration). Thus, the velocity of a chemical reaction is proportional to the product of the concentration of the reactants.

chemical reaction equation    →   jednadžba kemijske reakcije

Chemical reactions are symbolically shown with chemical equations. On the left side of the equation we write formulas or substance symbols which enter the chemical reaction, reactants. On the right side formulas or substance symbols which emerge from the chemical reaction, products, are writen.

Each chemical reaction leads to an equilibrium which is moved more or less to one side (left or right). Because of that, in reversible reactions instead of = sign two opposite arrows are put

In order to write down certain chemical reaction equation all reactants and all products and their stechiometric proportions must be known. (See Chemical reaction balancing)