Ch.8 - Monoprotic Acid-Base EquilibriaWorksheetSee all chapters
All Chapters
Ch.1 - Chemical Measurements
Ch.2 - Tools of the Trade
Ch.3 - Experimental Error
Ch.4 + 5 - Statistics, Quality Assurance and Calibration Methods
Ch.6 - Chemical Equilibrium
Ch.7 - Activity and the Systematic Treatment of Equilibrium
Ch.8 - Monoprotic Acid-Base Equilibria
Ch.9 - Polyprotic Acid-Base Equilibria
Ch.10 - Acid-Base Titrations
Ch.11 - EDTA Titrations
Ch.12 - Advanced Topics in Equilibrium
Ch.13 - Fundamentals of Electrochemistry
Ch.14 - Electrodes and Potentiometry
Ch.15 - Redox Titrations
Ch.16 - Electroanalytical Techniques
Ch.17 - Fundamentals of Spectrophotometry
BONUS: Chemical Kinetics
Arrhenius Acids and Bases
Bronsted-Lowry Acids and Bases
Lewis Acids and Bases
Ka and Kb of compounds
Weak Acid-Base Equilibria
Ionic Salts of Weak Acids and Bases

The acid dissociation constant, Ka, and the base dissociation constant, Kb, determine the strengths of weak acids and weak bases respectively. 

Ka and Kb

Example #1: Associated with any weak acid or weak base is a Ka or Kb value respectively. 

Ka examines the strength of weak acids. 

Kb examines the strength of weak bases. 

Example #2: Consider two aqueous solutions of equal concentration. Which statement is true?

chlorous acid (HClO2, Ka = 1.1 x10 -2 ) and phenol (HC6H5O, Ka = 1.3 x10 -10)

a) HClO2 produces more [H3O+] than HC6H5O

b) HClO2 is basic compared with HC6H5O

c) HClO2 produces less [H3O+ ] than HC6H5O

d) HClO2 is a strong acid

e) ClO2– produces more [OH] than C6H5O

Ka and Kb Calculations

Example #3: Which of the following compounds has the strongest conjugate acid?

a) C2H5NH2        (Kb = 5.6 x 10-4)

b) H2NNH­2         (Kb =  1.3 x 10-6)

c)  NH3               (Kb =  1.75 x 10-5)

d)  HONH­2          (Kb = 1.1 x 10-8)

Example #4: At 0 oC, the ion product constant of water is 1.2x10–15. The pH of pure water at this temperature is:

a) 6.88

b) 7.00

c) 7.46

d) 7.56

Practice: A − is a weak base. Which equilibrium corresponds to the equilibrium constant Ka for HA?