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    Acid-Base Equilibria in Aqueous and Nonaqueous Solutions

    Published: Jan 1947

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    For uncharged proton acids in basic solvents of not too low dielectric constant the reaction Ax+SSH++Bx.........(1) takes place, the extent of the reaction depending on the strength of the acid Ax relative to the basic strength of the solvent S. The equilibrium constant for this reaction KAxS=CSH+CS·CBCAx.........(2) is usually expressed as the more commonly used dissociation constant Kc which includes the concentration of the solvent. KAxS·CS=CSH+CBCAx=Kc......(3) The constant Kc varies with ion concentration, and in the limited range of concentration where the Debye-Hückel theory applies the following equation may be used to determine the thermodynamic equilibrium constant [Kc]° logKc=log[Kc]o+Aμ.......(4) where A2=0.434ε2(DkT)32·πN1000 The values for A at 25 C. are: for water (dielectric constant D=78.54) 1.020, for methyl alcohol (D=31.5) 4.02, for ethyl alcohol (D=24.2) 5.97, and for butyl alcohol (D=17.4) 9.79. For more concentrated solutions no theoretical equation can be given, but Table I shows that the change in the equilibrium constant is of considerable magnitude.

    Author Information:

    Kilpatrick, Martin
    Professor of Chemistry, University of Pennsylvania, Philadelphia, Pa.

    Committee/Subcommittee: E01.02

    DOI: 10.1520/STP47879S