Linear Plot of Species versus pH
Mono Protic Weak Acid
Monoprotic acids, such as acetic or salicylic acid, have one pKa value and thus two species at various pH values. These forms are the free acid form, HA, and the salt form, A-. The concentration of each species can be calculated with the equations.
Equation 1 Fraction present as HA
Equation 2 Fraction present as A-
Some Examples
| Acid |
pKa1 |
| Acetic* |
4.76 |
| Boric |
9.24 |
| Lactic |
3.86 |
| Salicylic |
2.97 |
*Default for Graph above.
References
- Martin, A.N., Swarbrick, J. and Cammarata, A. 1970 Physical Pharmacy, 2nd Edition, Chapter 9 Ionic Equilbria, Tabel 9-1, Lea & Febiger, Philadelphia, PA