Lecture 15. Chem Equilibrium

Lecture 15. Chem Equilibrium - Chapter 12: Chemical...

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Unformatted text preview: Chapter 12: Chemical Equilibrium Chapter Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. 2004. Why Does Ionic Strength Affect Solubility? Why Solubility of PbI2 in KNO3 solution. Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Ionic Atmosphere Ionic What effect does ionic strength have What on the ionic atmosphere? on Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman The Debye-Hückel (or Ion-Cloud) Theory The Total charge in the ionic Total atmosphere is equal but of opposite sign to charge of central ion. central Modern Electrochemistry, Vol. 1, J. O’M. Bockris, A. K. N. Reddy; Plenum, New York, 1973. The Debye-Hückel (or Ion-Cloud) Theory The Modern Electrochemistry, Vol. 1, J. O’M. Bockris, A. K. N. Reddy; Plenum, New York, 1973. The Debye-Hückel (or Ion-Cloud) Theory The Modern Electrochemistry, Vol. 1, J. O’M. Bockris, A. K. N. Reddy; Plenum, New York, 1973. The Debye-Hückel (or Ion-Cloud) Theory The κ -1: effective thickness of the effective ion atmosphere surrounding the central ion. the Modern Electrochemistry, Vol. 1, J. O’M. Bockris, A. K. N. Reddy; Plenum, New York, 1973. The Debye-Hückel (or Ion-Cloud) Theory The Modern Electrochemistry, Vol. 1, J. O’M. Bockris, A. K. N. Reddy; Plenum, New York, 1973. Activity Coefficients (γ ) Activity aA+bB cC+dD c d c d AC AD [C]c gC [D]d gD K= a b = a b AA AB [A]a gA [B]b gB Daniel C. Harris, Exploring Chemical Analysis, 3rd ed., W.H. Freeman and Company, New York, 2005. Freeman Extended Debye-Hückel Equation Extended -0.51z 2 m log g = am 1+ 305 pm Good for µ ≤ 0.1 M Good α is hydrated radius of ion of interest is Ionic Strength (µ ) Ionic A measure of the total concentration of ions in measure solution. solution. 1 1 2 2 µ = å c iz i = (c1z1 + c 2z 2 + ...) 2 2i 2 Extended Debye-Hückel Equation Extended -0.51z 2 m log g = am 1+ 305 pm Good for µ ≤ 0.1 M Good α is hydrated radius of ion of interest is What about neutral molecules? Hydrated Hydrated Radius (α) Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Daniel Freeman and Company, New York, 2001. Freeman Ionic Strength, Ion Charge and Ion Size Ionic -0.51z 2 m log g = am 1+ 305 pm Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Concentration Dependence of Activity Coefficients Concentration Morf, W. E. The Principles of Ion-Selective Electrodes and of Membrane Transport; Morf, The Elsevier: New York, 1981. Elsevier: High Ionic Strength (>1M) High Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman The Big Exception The pH = - log aH + = - log ([H + ]gH + ) General Trends General Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. 2004. ...
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