Reaction Equilibrium in Aqueous Solutions

For a chemical or ionic equilibrium occurring in an aqueous solution with reaction equilibrium represented by  

Recalling that the chemical potential of an aqueous species can be represented by reference to a standard state or  

The thermodynamic equilibrium constant for this reaction is defined as  

As an example, let us calculate the thermodynamic equilibrium constant for the ionic equilibrium representing the dissociation of the bisulfate ion in aqueous solution given by  

This value, calculated with the standard fre energies of formation compiled by the NBS, represents the dissociation constant of the bisulfate ion at 25 Celsius (298.15 Kelvins) which is the reference temperature for their compilation. The accepted value of this equilibrium constant as given in Robinson and Stokes (1) determined experimentally is. 0104 i. 0003. The experimental result agrees quite well with that calculated from the standard free energies of formation and the difference between the results represents a difference in a of 

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