Acetic Acid Titration: Model for Reversible, Monovalent Equilibrium Ligand Binding Reactions Go back
Graphical Analyses Equilibrium Reactions Chemical & Mathematical Formulation Quantitative Relationships Exercises

Graphical Analyses of Reversible Monovalent Ligand Binding Systems: Top

"Rollover" graphical Representations
"Y" vs. "X"		 Mathematical Relationships:
 "Y" vs. f("X")
Henderson-Hasselbalch Plot: 
pH  vs. Yd or Ya
Henderson-Hasselbalch Plot: 
pH vs. log (Yd/Ya)
Desaturation Plot: 
Yd or Ya vs. pH
Desaturation Plot: 
Yd or Ya vs. [H+]
(log scale)

Rectangular Hyperbolic
Saturation Plot: 
Ya or Yd vs. [H+] 
(linear scale)
Click here to open an Excel spreadsheet with various acetic acid titration charts. 

Roll mouse over links at left to view static images below of different acetic acid titration plots, or click on the links to open dynamic popup charts.

Acetic Acid Titration Equilibrium Reactions: Top

1-Step Dissociation Reaction 
desaturation, ionization 

In the one-step dissociation (or ionization or desaturation) reaction, protonated  or saturated acetic acid releases an H+ (hydronium) ion converting into deprotonated or desaturated  acetate ion. 
The "dissociation fraction" (Yd) of dissociated acetic acid at equilibrium is proportional to the equilibrium H+ concentration, [H+], and acetic acid's dissociation equilibrium constant (Kdn).

1-Step Association Reaction
saturation, protonation

In the one-step association (or protonation or saturation) reaction, deprotonated  or desaturated  acetate ion binds an H+ (hydronium) ion converting into protonated or saturated acetic acid.  
The "association fraction" or saturation fraction (Ya) of associated acetic acid at equilibrium is proportional to the equilibrium H+ concentration, [H+], and acetic acid's association equilibrium constant (Kan).
Dissociation constant: Kdn Association constant: Kan

acetic acid 

acetate

acetate

acetic acid


Key Chemical and Mathematical Formulation: Top
[ CH3COOH] = [HAc] = acetic acid equilibrium concentration
[ CH3COO-] = [Ac-] = acetate equilibrium concentration
Co = [Ac- ] + [ HAc ] = the total equilibrium concentrations of acetic acid plus acetate.
Yd = the "dissociated fraction," the total fraction of all molecules in solution that are ionized or deprotonated.
Ya = the "associated " or "saturated fraction," the total fraction of all molecules in solution that are protonated acetic acid molecules.
Yd + Ya = 1:  The fractions of all molecules have to add up to one. 
Key Quantitative Relationships Derived from the Equation for the Equilibrium Dissociation Constant, Kdn Top
 Note: pKdn = -log(Kdn); Kdn = 10-pKdn
pH = -log[H+]; & [H+] = 10-pH
 
Recommended Exercises: Top
1.   Prove that  Kdn = [H+]50%, where [H+]50% = the H+ concentration at 50% saturation.  
Hint: Determine [H+] at Ya = 0.5 or Yd = 0.5 (i.e., at "50% saturation").
2.  

Prove that   where

3.  

Prove that Kan = 1/[H+]50%, where [H+]50% = H+ concentration at 50% saturation.  
Hint: Determine [H+] at Ya = 0.5 or Yd = 0.5 (i.e., at "50% saturation").

Graphical Analyses Equilibrium Reactions Chemical & Mathematical Formulation Quantitative Relationships Exercises
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© Duane W. Sears
Revised: March 26, 2007