begin mathsize 48px style log space f equals negative A z squared square root of I space end style

I = Ionic Strength ; z =  Charge number of  an ionic specie ; f = Activity coefficient ;

A= A  constant that depends on temperature.
(A is assumed to be 0.509 mol-1/2 kg
-1/2 which corresponds to water at 25oC)






Activity coefficient of an ionic specie is related to it's ionic strength. You may use our ionic strength calculator: visit. It is to be kept in mind that the calculated f corresponds to it's activity coefficient in water at 25oC, since A is assumed to be 0.509 mol-1/2 kg-1/2. A is dependent on temperature and solvent. 

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