CHEMISTRY GLOSSARY

electrolytic cell    →   elektrolitska ćelija

Electrolytic cell is an electrochemical cell that converts electrical energy into chemical energy. The chemical reactions do not occur spontaneously at the electrodes when they are connected through an external circuit. The reaction must be forced by applying an external electric current. It is used to store electrical energy in chemical form (rechargeable battery). It is also used to decompose or produce (synthesise) new chemicals by the application of electrical power. This process is called electrolysis, e.g., water can be decomposed into hydrogen gas and oxygen gas. The free energy change of the overall cell reaction is positive.

erbium    →   erbij

Erbium was discovered by Carl Gustaf Mosander (Sweden) in 1843. Named after Ytterby, a village in Sweden. It is soft, malleable, silvery metal. Reacts slowly with water. Dissolves in acids. Metal ignites and burns readily. Erbium is found with other heavier rare earths in xenotime and euxenite. Erbium oxide is used in ceramics to obtain a pink glaze. Also a few uses in the nuclear industry and as an alloying agent for other exotic metals.

ether    →   eter

Ethers are organic compounds with a formula R-O-R, where R is not equal to H. They may be derived from alcohols by elimination of water, but the major method is catalytic hydration of olefins. They are volatile highly flammable compounds; when containing peroxides they can detonate on heating. The term ether is often used synonymously with diethyl ether.

europium    →   europij

Europium was discovered by Eugene Demarcay (France) in 1896. Named for the continent of Europe. It is soft, silvery-white metal. Extremely reactive with oxygen and water. Europium is obtained from monazite sand, which is a mixture of phosphates of calcium, thorium, cerium and most other rare earths. Used with yttrium oxide to make red phosphors for colour televisions.

experiment    →   eksperiment

Experiment is direct observation under controlled conditions. Most experiments involve carefully changing one variable and observing the effect on another variable (for example, changing temperature of a water sample and recording the change volume that results).

Fahrenheit scale    →   Fahrenheitova skala

Fahrenheit scale is the temperature scale in which 212 degrees is the boiling point of water and 32 degrees is the freezing point of water. The scale was invented in 1714 by the German physicist G.D. Fahrenheit (1686-1736).

32 °F = 0 °C
212 °F = 100 °C
1 °F =(5/9) °C
T(°C) = (5/9)[T(°F) - 32]
T(°F) = (9/5)T(°C) + 32

fatty acid    →   masna kiselina

Fatty acids are aliphatic monocarboxylic acids characterized by a terminal carboxyl group (R-COOH). The higher members of this series of acids occur in nature in the combined form of esters of glycerol (fats), and hence all acids of this family are called fatty acids. Natural fatty acids commonly have a chain of 4 to 28 carbons (usually unbranched and even-numbered), which may be saturated or unsaturated. The most important of saturated fatty acids are butyric (C4), lauric (C12), palmitic (C16), and stearic (C18). The most common unsaturated acids are oleic, linoleic, and linolenic (all C18).

The physical properties of fatty acids are determined by the chain length, degree of unsaturation, and chain branching. Short-chain acids are pungent liquids, soluble in water. As the chain length increases, melting points are raised and water-solubility decreases. Unsaturation and chain branching tend to lower melting points.

Fischer-Tropsch process    →   Fischer-Tropschov postupak

Fischer-Tropsch process is an industrial method of making hydrocarbon fuels from carbon monoxide and hydrogen. The process was introduced in 1933. and used by Germany in World War II. to produce motor fuel. Hydrogen and carbon monoxide are mixed in the ratio 2:1 (water gas was used with added hydrogen) and passed at 200 °C over a nickel or cobalt catalyst. The resulting hydrocarbon mixture can be separated into a higher-boiling fraction for Diesel engines and a lower-boiling petrol fraction. The petrol fraction contains a high proportion of straight-chain hydrocarbons and has to be reformed for use in motor fuel. Alcohols, aldehydes, and ketones are also present. The process is also used in the manufacture of SNG from coal. It is named after the German chemist Franz Fischer (1852-1932) and the Czech Hans Tropsch (1839-1935).

fossil fuel    →   fosilno gorivo

Fossil fuels (coal, oil, and natural gas) are the fuels used by man as a source of energy. They are formed from the remains of living organisms and all have a high carbon or hydrogen content. They have value as fuels on the exothermic oxidation of carbon to form carbon dioxide

and the oxidation of hydrogen to form water

fuel cell    →   gorivi članak

Fuel cell is a device that converts chemical energy into electrical energy. It is different from a battery in that the energy conversion continues as long as fuel and oxidising agent are fed to the fuel cell; that is, in principle indefinitely. (A battery is manufactured with a limited amount of chemicals, and it is exhausted when all the chemicals have reacted.) It is a galvanic cell where spontaneous chemical reactions occur at the electrodes. The fuel is oxidised at the anode, and the oxidising agent (almost always oxygen or air) is reduced at the cathode. Presently, the most commonly used fuel is hydrogen. More conventional fuels (e.g., petrol or natural gas) must be converted (reformed) into hydrogen before they can be utilised in a fuel cell.

Some fuel cells employ an aqueous solution as electrolyte, that can be either acidic or basic (alkaline), or an ion-exchange membrane soaked in aqueous solution can act as the electrolyte. These fuel cells operate at relatively low temperatures (from room temperature to not much above the boiling point of water). Some fuel cells employ molten salts (especially carbonates) as electrolytes and have to operate at temperatures of several hundred degrees centigrade (Celsius). Others employ ionically conductive solids as electrolyte and must operate close to 1 000 °C.