Tables of values of the heat of formation, !1H.f°; free energy of formation, !1Ff o; logarithm of the equilibrium constant of formation, loglOKf; free-energy function, (FO -Ho) / T; heatcontent function, (ljO -: Ho)/ T; entropy, So; heat content, (l{O -Ho), and heat capacity, C~, are given from 0° K to high temperatures for the following gaseous substances: F, F z, FzO, CI, Ch, CIO z, Cl,O, CIF, CIF3, Br, Brz, BrF, BrF5, BrCI, I , Jz, IF, IF5, IF7, lei and IBr. The data used in preparin g thc tables are discussed in detail.
The a va ilable data on the thermodynamic properties of the elem ents lithium, sodium, p otassi um, rubidium, a nd cesium have been analyzed, a nd selected values of these properties are presented in tabular form . The tables inclu de valu es of the free-energy function, (F°-HO)/ T ; heat-content function, (H O-H a) / T; entropy, S o; heat content, (l-I°-H a) ;heat capacity, C~; heat of formation, !!.l--Ij" ; free energy of format ion, !!.Fj"; and logarithm of tlle equilibrium constant of formation, log Kf , for the solid, the liquid, and the monatomic a nd diatomic gases as a function of temperature from 0° K to high temperatures. . IntroductionAs part of a general program on the collection, analysis, and compila tion of data on the ch emical thermodynamic proper ties of chemical substances [1 , 2),3 a survey has bee n m ade of aU of the available data relatin g to the thermodynamic properties of t he alkali m etals, li thium, odium, potassium, rubidium, and cesium. There is co nsid erable in terest in the usc of these m etals in chemical synt he e , as well as in their use as heat-transfer media. A large amount of new data has become available sin ce tbe early summaries of Gordon [3] a nd K elley [4,5]; it is believed that a complete s ummary of t he data on t hese clements presented in a convenient tabular form will be very useful to enginccrs, physicists, a nd chemists engaged in pr oblems involvin g t hese substances. This s urvey will also indicate gaps a nd weaknesses in t he prese nt state of our knowledge with r espect to these s ubstanc es and indicate areas r eq uirin g addi tional r esearch. Units and Standard StatesThe calorie used in t hese calculations is the thermochemical calorie, defined by the relation : 1 cal = 4.1840 abs j. The other cons tan ts are those given by Wagman et al. [6]. The ice point, 0° C , is taken as 273.16° K [71. The chemical atomic weights [8] used are: Li, 6.940; Na, 22.99 1; K , 39.10; Rb , 85.48; Cs, 132.91. For gases t he standard state chosen is the hy pothetical ideal gas at I-atmosphere pressure. For solids and liquids t he standard state is taken as tb e substance under I-atmosphere pressure (o r sat ura ted vapor pressure, if this is greater). As is custom ary, nuclear spin a nd isotopic mixing contributions to th e free-energy function and entropy are omitted; all values are for t he naturally occurring isotopic mixt ure. The ymbols used for thermodynamic quantities arc those used previously [1,2]. 83 . Calculation of the Thermodynamic Functions Monatomic GasesThe translational contributions to the thermodynamic fun ctions of the monatomic gases Li, N a, K , Rb , and Os were calculated by use of t be equaLions given by Wagman et al. [6] (corrected for t he new defini tion of the thermochemical caloric). The additional contributions due to electronic excitation are easily obLained in terms of t he par tition function , Q, a nd tbe derived fun ctions Q' a nd Q" Q' = ~i gi (~dkT) e-E .lk T These conlributions were evalu ated by direct summation. Th e energy level...
In spite of the experimental failures to prepare praseodymium tetrafluoride, there is strong evidence for its possible formation to be found by calculating the equilibrium constants for some of the reactions by which this compound might be prepared.
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