Equilibrium principles in aqueous systems are limited to qualitative descriptions and/or calculations involving:

• relative concentrations of dissolved species
• sparingly soluble ionic solids
  • relating solubility to Ks
  • solubility of solids in water and in solutions already containing one of the ions A or B (a common ion) or due to the formation of a complex ion, or the reaction of a basic anion with added acid
  • predicting precipitation or dissolution
• acidic and basic solutions (includes buffers)
  • acid/base strength, Ka (pKa)
  • concentration of species present in weak acidic and/or basic solutions (includes buffers)
  • relating concentration of species to pH and conductivity
  • titration curves to represent an acid-base system including selection of indicators (titrations of weak acids with weak bases are excluded). 

Sparingly soluble ionic solids are limited to AB, A2B and AB2 types where neither of the ions A nor B reacts further with water. 

Acidic and basic solutions are monoprotic acids, bases, salts, and buffers (those in which the extent of reaction is small so that the equilibrium concentration of a dissolved weak acid or base can be approximated by the initial concentration).