CHEMISTRY GLOSSARY
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.
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.
| Water supply classification | |
|---|---|
| Hardness | Concentration of Calcium carbonate (mg/L) |
| Soft Water | 0 to 75 |
| Medium Hard Water | 75 to 150 |
| Hard Water | 150 to 300 |
| Very Hard Water | over 300 |
work → rad
Work is the energy required to move an object against an opposing force. Work is usually expressed as a force times a displacement.
When a constant force F acts on a point-like object while the object moves through a displacement s, the force does work W on the object. If force and displacement are at a constant angle Θ to each other, the work is expressed by the scalar product of these two vectors:
When the force F on a point-like object is not constant that is, it depends on the position of the object, the work done by force while object moves from initial position with coordinates (xi, yi, zi) to final position with coordinates (xf, yf, zf)is given by expression:
Where Fx, Fy and Fz are scalar components of the force.
SI unit for work is joule (J); 1 J = 1 Nm = 1 kg m2 s-2. The electron-volt (eV) is commonly used in atomic and nuclear physics.
Citing this page:
Generalic, Eni. "Kill to Survive scan vf." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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