5. Acid-Base Equilibria and Activity

  1. Brian M. Tissue

Published Online: 7 JUN 2013

DOI: 10.1002/9781118647042.ch5

Basics of Analytical Chemistry and Chemical Equilibria

Basics of Analytical Chemistry and Chemical Equilibria

How to Cite

Tissue, B. M. (2013) Acid-Base Equilibria and Activity, in Basics of Analytical Chemistry and Chemical Equilibria, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781118647042.ch5

Author Information

  1. Virginia Tech, Department of Chemistry, Blacksburg, VA, USA

Publication History

  1. Published Online: 7 JUN 2013
  2. Published Print: 12 JUL 2013

ISBN Information

Print ISBN: 9780470592083

Online ISBN: 9781118647042



  • activity;
  • formal equilibrium constant;
  • ionic strength;
  • Kw;
  • thermodynamic equilibrium constant;
  • water;
  • weak acids;
  • weak bases


This chapter reviews acids, bases, and the equilibria of weak acids and weak bases in water. It introduces the concepts of ionic strength and activity. Activity coefficients are used to correct the thermodynamic equilibrium constant, K, to generate the formal equilibrium constant, K'. The K' values provide a more realistic description of real solutions. Kw is called the ion product, dissociation constant, or ionization constant of water. It is a measured thermodynamic quantity that is temperature dependent. For most monoprotic weak acid calculations, ionic strength effects are not significant. Ionic strength effects are often neglected to predict equilibrium concentrations of neutral weak acids and neutral weak bases in water. For other types of equilibria very significant differences are often found between the ideal case and the behavior in real, that is, nonideal, solutions.