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Fluctuation functions in aqueous NaCl and urea

TitleFluctuation functions in aqueous NaCl and urea
Publication TypeJournal Article
Year of Publication2005
AuthorsSiu, D, Koga, Y
JournalJournal of Physical Chemistry B
Volume109
Pagination16886-16890
Date PublishedSep
Type of ArticleArticle
ISBN Number1520-6106
Keywords25-DEGREES-C, H2O, LIQUID WATER, MODEL, PARTIAL MOLAR FLUCTUATIONS, PERCOLATION, SODIUM-CHLORIDE, SYSTEMS, VOLUMETRIC PROPERTIES
Abstract

We earlier devised a set of fluctuation functions that provide relative qualitative differences of the amplitude (intensity) and the wavelength (extensity) of fluctuations in entropy and volume and the entropy-volume cross fluctuations. We discuss the mixing schemes in aqueous NaCl and urea using these fluctuation functions. Our earlier studies by using the second and third derivatives of Gibbs energy indicated that their effects on H2O are qualitatively different. An NaCl hydrates 7.5 molecules of H2O but leaves the bulk H2O away from the hydration shell unperturbed. Urea, on the other hand, connects onto the hydrogen bond network of H2O but retards the degree of fluctuation inherent in H2O. The behavior of the fluctuation functions calculated here are consistent with the above mixing schemes. Furthermore, urea was found to reduce the wavelength of fluctuation more strongly than NaCl.

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