Proper quotient of activities

Qixn consists of a factor for each reactant and product. Each factor is the activity raised to the power of the stoichiometric number Vj. Since the value of v is positive for a product and negative for a reactant, Qrxn is a quotient in which the activities of the products appear in the numerator and those of the reactants appear in the denominator, with each activity raised to a power equal to the corresponding stoichiometric coefficient in the reaction equation. Such a quotient, with quantities raised to these powers, is called a proper quotient. The reaction quotient is a proper quotient of activities. 

We can readily derive a relation between Ks and the molalities of the ions in the saturated solution by treating the dissolved salt as a single solute substance, B. We write the equiUbrium in the form B (s) B(sln), and write the expression for the solubility product as a proper quotient of activities ... 

Note that the argument of the logarithm is a proper quotient of fugacity and activity for the electrode reaction if the presence of the electrons is ignored in constructing the quotient. From Eq. (17.33) we can calculate the potential, relative to SHE, of a hydrogen electrode at which/h2 and h+ have any values. 

The thermodynamic equilibrium constant K is the proper quotient of the activities of species in reaction equilibrium. At typical temperatures and pressures, an activity cannot be... 

Notice that at standard state conditions, all activities are unity, the value of the quotient within the parentheses in Equahon 5.39 is 1, and with those conditions, the AG of the reaction is properly the AGi, the standard state value for the free energy change of the reaction. 

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