Acid Base Equilibria

Content
● Acid dissociation constants, Ka and the use of pKa
● Base dissociation constants, Kb and the use of pKb
● The ionic product of water, Kw
● pH: choice of pH indicators
● Buffer solutions
Learning Outcomes
Candidates should be able to:
(a) explain qualitatively the differences in behaviour between strong and weak acids and bases in terms of the extent of dissociation
(b) explain the terms pH; Ka ; pKa ; Kb ; pKb ; Kw and apply them in calculations, including the relationship
Kw =KaKb
(c) calculate [H+ (aq)] and pH values for strong acids, weak monobasic (monoprotic) acids, strong bases, and weak monoacidic bases [Calculations involving weak acids/bases will not require solving of quadratic equations]
(d) describe the changes in pH during acid-base titrations and explain these changes in terms of the strengths of the acids and bases
(e) explain the choice of suitable indicators for acid-base titrations, given appropriate data
(f) (i) explain how buffer solutions control pH
(ii) describe and explain their uses, including the role of H2CO3 /HCO3– in controlling pH in blood
(g) calculate the pH of buffer solutions, given appropriate data