CHEMISTRY GLOSSARY

water softener    →   omekšivač vode

Water softeners are substances which help remove constant water hardness. It reacts with calcium and magnesium salts, creating compounds that do not react with soap.

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.

water purification    →   pročišćavanje vode

Water purification is a procedure of harmful substances removal in order to obtain pure drinking-water.

water softening    →   omekšavanje vode

Water softening is a process in which calcium and magnesium ions are removed from water. It is usually done by ion exchanger which exchanges removed ions with sodium ones.

ion-product constant    →   ionski produkt vode

The ion-product constant. For the reaction:

the equilibrium expression would be:

Note that all pure liquid terms are omitted, hence H₂O does not appear in the denominator. At 25 °C

water ion product    →   ionski produkt vode

Water ion product (K_w) is a concentration product of hydrogen and hydroxide ions. For the reaction:

the equilibrium expression would be:

Note that all pure liquid terms are omitted, hence H₂O does not appear in the denominator. At 25 °C, K_w = 1.0×10^-14 mol²dm^-6 = (K_a)(K_b)

water hardness    →   tvrdoća vode

Hardness is defined as the concentrations of calcium and magnesium ions expressed in terms of calcium carbonate. These minerals in water can cause some everyday problems. They react with soap and produce a deposit called soap curd that remains on the skin and clothes and, because it is insoluble and sticky, cannot be removed by rinsing.

Hard water may also shorten the life of plumbing and water heaters. When water containing calcium carbonate is heated, a hard scale is formed that can plug pipes and coat heating elements. Scale is also a poor heat conductor. With increased deposits on the unit, heat is not transmitted to the water fast enough and overheating of the metal causes failure. Build-up of deposits will also reduce the efficiency of the heating unit, increasing the cost of fuel.

There are two types of water hardness, temporary and permanent.

Temporary Hardness is due to the bicarbonate ion, HCO₃^-, being present in the water. This type of hardness can be removed by boiling the water to expel the CO₂, as indicated by the following equation:

Permanent hardness is due to calcium and magnesium nitrates, sulphates, and chlorides etc. This type of hardness cannot be eliminated by boiling.

aqueous solution    →   vodena otopina

Aqueous solutions are those solutions where water is the solvent. An aqueous solution found in an equation describing a chemical reaction is denoted by the state symbol, (aq).

conductivity    →   vodljivost

Conductivity is a measure of the ability of a material to conduct electric current.

crystal water    →   kristalna voda

Crystal water is water contained in certain salt crystals. It can be removed by heating. Crystals that contain crystal water are called hydrated and their salts hydrates.