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1.23.5: Water: Self-Dissociation

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    397802
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    A significant contribution to the chemistry of aqueous solutions stems from the self dissociation of water(\(\ell\))(see also \(\mathrm{D}_{2}\mathrm{O}(\ell\)) [1]). At \(298.15 \mathrm{~K}\) and ambient pressure, \(\mathrm{pK}_{\mathrm{a}} equals 14.004 [2]. Olofsson and Hepler [3] recommended a ‘best value’ for the standard enthalpy of self dissociation at ambient pressure and \(298.15 \mathrm{~K}\) equal to \(55.81 \mathrm{~kJ mol}^{-1}\) [4,5]. Hepler and colleagues recommend a best value for\(\Delta_{\mathrm{d}} C_{\mathrm{p}}^{0}\) equal to \(- 215 \mathrm{~J K}^{-1} \mathrm{~mol}^{-1}\) [5]; see also [6-8] together with [1] for details characterizing \(\mathrm{D}_{2}\mathrm{O}\).

    The standard volume of self-dissociation for water(\(\ell\)) at \(298 \mathrm{~K}\) is negative, approx. \(- 20 \mathrm{cm}^{3} \mathrm{~mol}^{-1}\), decreasing with increase in temperature [8,9].

    An extensive literature describes the thermodynamics of self-dissociation of water in binary liquid mixtures [11]; see also [12] for \(\mathrm{D}_{2}\mathrm{O}\).

    Footnotes

    [1] A. K. Covington, R. A. Robinson and R. G. Bates, J. Phys. Chem., 1966, 70, 3820.

    [2] A. K. Covington, M. I. A. Ferra and R. A. Robinson, J. Chem. Soc. Faraday Trans.,1,1977,73,1721.

    [3] G. Olofsson and L. G. Hepler, J. Solution Chem.,1975,4,127.

    [4] G. Olofsson and I. Olofsson, J. Chem. Thermodyn.,1973, 5, 533; 1977, 9, 65.

    [5] O. Enea, P. P. Singh, E. M. Woolley, K. G. McCurdy and L. G. Hepler, J. Chem. Thermodyn., 1977, 9,731.

    [6] G. C. Allred and E. M. Woolley, J. Chem. Thermodyn..,1981, 13, 147.

    [7] P. P. Singh, K. G. McCurdy, E. M. Woolley and L. G. Hepler, J. Solution Chem., 1977,6,327.

    [8] J. J. Christensen, G. L .Kimball, H. D. Johnston and R. M. Izatt, Thermochim. Acta,1972,4,141.

    [9]

    1. D. A. Lown, H. R. Thirsk and Lord Wynne-Jones, Trans. Faraday Soc., 1968, 64,2073.
    2. F. J. Millero, E. V. Hoff and L. Kahn, J. Solution Chem.,1972,1,309.

    [10] J. P. Hershey, R. Damasceno and F. J. Millero, J. Solution Chem.,1984,13,825.

    [11]

    1. DMSO + water(\(\ell\)); A. K. Das and K. K. Kundu, J. Chem. Soc. Faraday Trans.1,1973, 69,730.
    2. \(\left(\mathrm{CH}_{3}\right)_{3}\mathrm{COH} + \text { water}(\ell)\); H. Gillet., L. Avedikian and J.-P. Morel, Can. J.Chem.,1975, 53,455.
    3. MeOH + water(\(\ell\)); C.H.Rochester, J. Chem. Soc., Dalton Trans.,1972,5.
    4. Alcohol + water(\(\ell\)); E. M. Woolley, D. G. Hurkot and L. G. Hepler, J. Phys. Chem., 1970,74,3908.
    5. \(\mathrm{CH}_{3}\mathrm{CN} + \text { water}(\ell)\); U. Mandal, S. Bhattacharya and K. K. Kundu, Indian J. Chem. Sect. A,1985,24,191.
    6. E. M. Woolley, and L.G.Hepler, Anal. Chem.,1972,44,1520.
    7. Urea+water; A. K. Das and K. K. Kundu, J. Phys.Chem.,1975,79,2604.

    [12] R. E.George and E. M. Woolley, J. Solution Chem.,1972,1,279.


    This page titled 1.23.5: Water: Self-Dissociation is shared under a Public Domain license and was authored, remixed, and/or curated by Michael J Blandamer & Joao Carlos R Reis.

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