begin mathsize 36px style K subscript a equals fraction numerator alpha squared C over denominator left parenthesis 1 minus alpha right parenthesis end fraction semicolon space p K subscript a equals space minus log K subscript a end style

Ka =  Acid Dissociation Constant ; C = Concentration of the Acidic Soluiton ;

α = Degree of dissociation of the acid

 

pKa

α

C

 
The ionization of an acid in water measures the relative strength of the acid. The Ka is simply the equilibrium constant for the ionization of an acid HA into H+ and A- . It can be written that Ka  [H+][A- ]/[HA]. Considering the degree of dissociation to be α we can easily establish the formula involving α , C (=concentration of the solution) and Ka , which is written above. It can be inferred that a higher value of Ka resemble stronger acid. Thus a lower value of pKa which -logKa will resemble a stronger acid. Here is a table of pKa Values:
 

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