1.23.5: Water: Self-Dissociation
- Page ID
- 397802
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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]
- D. A. Lown, H. R. Thirsk and Lord Wynne-Jones, Trans. Faraday Soc., 1968, 64,2073.
- 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]
- DMSO + water(\(\ell\)); A. K. Das and K. K. Kundu, J. Chem. Soc. Faraday Trans.1,1973, 69,730.
- \(\left(\mathrm{CH}_{3}\right)_{3}\mathrm{COH} + \text { water}(\ell)\); H. Gillet., L. Avedikian and J.-P. Morel, Can. J.Chem.,1975, 53,455.
- MeOH + water(\(\ell\)); C.H.Rochester, J. Chem. Soc., Dalton Trans.,1972,5.
- Alcohol + water(\(\ell\)); E. M. Woolley, D. G. Hurkot and L. G. Hepler, J. Phys. Chem., 1970,74,3908.
- \(\mathrm{CH}_{3}\mathrm{CN} + \text { water}(\ell)\); U. Mandal, S. Bhattacharya and K. K. Kundu, Indian J. Chem. Sect. A,1985,24,191.
- E. M. Woolley, and L.G.Hepler, Anal. Chem.,1972,44,1520.
- 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.