begin mathsize 36px style p H space equals space p K subscript a space plus log fraction numerator left square bracket C B right square bracket over denominator left square bracket C A right square bracket end fraction end style

Ka =  Acid Dissociation Constant ; [CB] = Concentration of the Conjugate Base ;

[CA] = Concentration of the Conjugate Acid; [H+] = Hydrogen Ion Concentration

pH = -log[H+] ; pKa = -logKa

pKa

pH

CA

CB

 
This calculator is valid for a buffer of a weak acid and it's conjugate base of the same system. For example if a system contains both CH3COOH and CH3COONa then the pH of this buffer can be calculated. Note that here [CH3COOH] = [CA] and [CH3COONa] = [CB]. This equation is also known as Henderson-Hasselbalch equation. 
 

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