Bromine standard entropies

The standard entropy of a substance in the gas phase is greater than the standard entropy of the same substance in either the liquid or solid phase (examples are water, bromine, and iodinej. 

Various Physical Properties.—Radical cations of 2,5-dialkylthiothiophens have been obtained and their e.s.r. spectra interpreted in terms of unequally populated rotational isomers. The mass spectra of some simple thiophens and some azines derived from 2-acetyl- and 2-formyl-thiophens have been obtained. Molecular ion isomerizations occurring in 3-phenylthiophen and two brominated derivatives have been followed in both slow and fast reactions using C-labelling. Affinities, standard heats, and standard entropies of dyeing of some thiophen-containing azo dyes have been... 

Which substance in each of the following pairs would you expect to have the higher standard molar entropy at 298 K Explain your reasoning, (a) Iodine vapor or bromine vapor ... 

The standard potentials of bromine and iodine have been determined by somewhat similar methods with bromine the results are expressed in terms of two alternative standard states, viz., the gas at 1 atm. pressure or the pure liquid. The standard state adopted for iodine is the solid state, so that the solution is saturated with respect to the solid phase. The acandard potential of fluorine has not been determined by direct experiment, but its value has been calculated from free energies derived from thermal and entropy data. ... 

Rubber Company Handbook (Weast, 1987) is one of the more commonly available sources. More complete sources, including some with data for a range of temperatures, are listed in the references at the end of the chapter. Note that many tabulations still represent these energy functions in calories and that it may be necessary to make the conversion to Joules (1 cal = 4.1840J). Because of the definition of the energy of formation, elements in their standard state (carbon as graphite, chlorine as CI2 gas at one bar, bromine as Br2 liquid, etc.) have free energies and enthalpies of formation equal to zero. If needed, the absolute entropies of substances (from which AS may be evaluated) are also available in standard sources. 

Trouton s rule states that for many liquids at their normal boiling points, the standard molar entropy of vaporization is about 88 I/mol-K. (a) Estimate the normal boiling point of bromine, Br2, by determining AH for Br2 using data from Appendix C. Assume that AHJ p remains constant with temperature and that Trouton s rule holds, (b) Look up the normal boiling point of Br2 in a chemistry handbook or at the WebElements Web site (www.webelements.com). 

Use the values of standard molar entropies in Appendix K to calculate the entropy change for the vaporization of one mole of bromine at 25°C. 

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