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For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
F is a natural trace radioisotope produced by cosmic ray spallation of atmospheric argon as well as by reaction of protons with natural oxygen: 18 O + p → 18 F + n. [53] Other radioisotopes have half-lives less than 70 seconds; most decay in less than half a second. [ 54 ]
Reactions with elemental fluorine are often sudden or explosive. Many substances that are generally regarded as unreactive, such as powdered steel, glass fragments, and asbestos fibers, are readily consumed by cold fluorine gas. Wood and even water burn with flames when subjected to a jet of fluorine, without the need for a spark. [12] [13]
Out of the four stable halogens, only fluorine and chlorine have reduction potentials higher than that of oxygen, allowing them to form hydrofluoric acid and hydrochloric acid directly through reaction with water. [17] The reaction of fluorine with water is especially hazardous, as an addition of fluorine gas to cold water will produce ...
The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
Fluorine-18 (18 F, also called radiofluorine) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96.7% of the time and electron capture 3.3% of the time.
Fluorine solidifies at −220 °C (−363 °F) [5] into a cubic structure, called beta-fluorine. This phase is transparent and soft, with significant disorder of the molecules; its density is 1.70 g/cm 3. At −228 °C (−378 °F) fluorine undergoes a solid–solid phase transition into a monoclinic structure called alpha-fluorine.
Fluorine cycle: F fluxes [1] are in Tg/yr and reservoir data [2] is in mg/kg. The major mechanisms that mobilize fluorine are chemical and mechanical weathering of rocks. Major anthropogenic sources also include industrial chemicals and fertilizers, brick manufacturing, and groundwater extra