Fluorinated gases

The only example of xenon in a fractional oxidation state, +, is the bright emerald green paramagnetic dixenon cation, Xe [12185-20-5]. Mixtures of xenon and fluorine gases react spontaneously with tiquid antimony pentafluoride in the dark to form solutions of XeF+ Sb2 F, in which Xe is formed as an iatermediate product that is subsequently oxidized by fluorine to the XeF+ cation (83). Spectroscopic studies have shown that xenon is oxidized at room temperature by solutions of XeF+ ia SbF solvent to give the XE cation (84). 

The application of liquid dispersion reac tors to the absorption of fluorine gases is described by Kohl and Riesenfeld (G .s Purification, Gulf, 1985, pp. 268-288). 

Cerium is separated from other rare-earth elements by an ion-exchange process in which it reacts with fluoride. This compound is then reduced with calcium metal (3Ca +2CeF — 2Ce + 3CaFj). Cerium can also be produced by the electrolysis of molten cerium salts. The metal ion collects at the cathode, and the chlorine or fluorine gases of the salt compound at the anode. 

However, the metal is slowly attacked by hydrofluoric acid and dissolves. Also, at ordinary temperatures, it is attacked by hydrogen fluoride and fluorine gases, forming niobium petafluoride, NbFs. 

Fluorinated gases (e.g., trifluoromethane (FC-23) and chlorofluoromethane (FC-22)) have been used to examine cerebral blood flow based on inflow and outflow kinetics, sometimes with pulsed delivery to facilitate compartmental analysis [401,402], The observation that HFB clears from tumors over a period of hours suggests this could provide insight into tissue perfusion [224,266],... 

It should be remembered that despite their high GWPs, fluorinated gases make a relatively minor contribution (ca. 1%) to the total GWP of mankind s emissions (see in this series, the chapters of R. Tuckett and A. Sekiya et at. devoted to the green house effect of SF5CF3 and to CFCs and HCFCs substitutes, respectively). 

In liquid ejectors or aspirators, the liquid is the motive fluid, so the gas pressure drop is low. Flow of slurries in the nozzle may be erosive. Otherwise, the design is as simple as that of the venturi. Kohl and Riesenfeld (Gas Purification, Gulf, 1985, pp. 268-288) describe the application of liquid dispersion reactors to the absorption of fluorine gases. 

Fig. 2. Relationship between decomposition temperature and decomposition rate for various fluorinated gases. O CF , A C2F6, SF6, CHF3, CC12F2, NF,.

Less than a year after Bartlett s report, a group at Argonne National Laboratory near Chicago prepared xenon tetrafluoride by reacting xenon and fluorine gases in a nickel reaction vessel at 400°C and 6 atm ... 

Nitrogen oxyfluoride gas, NOF, is formed by a reaction between nitrogen monoxide and fluorine gases. Write a balanced chemical equation for this reaction, and classify the reaction as one of the five major types. 

The Structural Indicator GHG emissions is [sic] defined as an index of greenhouse gas (C02, CH4, N20, HFC, PFC and SF6) emissions normalized by the base quantity in C02-equivalents (excluding land use changes and forestry). The base quantity is defined by the GHG emissions in the base year. The base year for the non-fluorinated gases (C02, CH4 and N20) is 1990, and 1995 for the fluorinated gases (HFC, PFC and... 

The use of cold-plasma can be applied to modify the fibres surface properties in two opposite directions, namely an increase in the hydrophilic character when the treatment is carried out in Argon or air [18, 76] and, on the contrary, the formation of a super-hydrophobic surface when fluorinated gases are used [18, 77-80]. A very recent publication illustrates clearly the latter approach [80]. In this study, paper sheets were plasma irradiated in the presence of CF4 and the surface modification characterized by XPS, ATR-FTIR as a function of the power parameters and the CF4 pressure. Interestingly, no significant difference was observed in the extent of modification to either side of the sheet. Figure 18.2 shows a typical XPS spectrum of one of these modified surfaces. 

A number of compounds containing the heavier noble gases, and especially xenon, have been prepared. One of these is xenon hexafluoride (XeF ), which can be prepared by heating a mixture of xenon and fluorine gases. XeF is a white crystalline soUd at room temperature and melts at about 325 K A mixture of 0.0600 g of Xe and 0.0304 g of F2 is sealed into a 100.0-mL bulb. (The bulb contains no air or other gases.) The bulb is heated, and the reaction above goes to completion. Then the sealed bulb is cooled back to 20.0°C. What will be the final pressure in the bulb, expressed in torr ... 

The three xenon fluorides, XeF2, XeF4, and XeFe, can all be prepared by direct reaction of xenon and fluorine gases under pressure, but conditions must be carefully controlled to obtain the desired product. Xenon tetrafluo-ride is produced in nearly quantitative amounts when a 1 5 mixture of Xe and F2 is heated to 400°C under 6 atm pressure. Xenon difluoride is formed by the same procedure if xenon is in excess. The preparation of XeFe requires 1 20 volume mixtures of xenon and fluorine at 250-300°C and 50-60 atm pressure. 

C02 accounted for the largest share of direct GHG emissions at 95 percent, followed by methane at four percent, and nitrous oxide and fluorinated gases accounting for the remaining one percent. 

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