1. Bases Sodium hydroxide Preferred IUPAC name Systematic name
Sodium oxidanide
Other names
Caustic soda Lye
Bases
Graphics Source: Wikipedia

2. Acid/Base Definitions
Arrhenius Model
Acids produce hydrogen ions in aqueous solutions
Bases produce hydroxide ions in aqueous solutions
Bronsted-Lowry Model
Acids are proton donors
Bases are proton acceptors
Lewis Acid Model
Acids are electron pair acceptors
Bases are electron pair donors

3. Dissociation of Strong Bases
MOH(s)  M+(aq) + OH-(aq)
Strong bases are metallic hydroxides
Group I hydroxides (NaOH, KOH) are very soluble
Group II hydroxides (Ca, Ba, Mg, Sr) are less soluble
pH of strong bases is calculated directly from the concentration of the base in solution

4. Reaction of Weak Bases with Water
The base reacts with water, producing its conjugate acid and hydroxide ion:
CH3NH2 + H2O  CH3NH3+ + OH- Kb = 4.38 x 10-4

5. Kb for Some Common Weak Bases
Formula
Conjugate Acid Kb
Ammonia 
 NH3
 NH4+
 1.8 x 10-5 
 Methylamine
 CH3NH2
 CH3NH3+
 4.38 x 10-4 
 Ethylamine
 C2H5NH2
 C2H5NH3+
 5.6 x 10-4 
 Diethylamine
 (C2H5)2NH
 (C2H5)2NH2+
 1.3 x 10-3 
 Triethylamine
  (C2H5)3N
  (C2H5)3NH+
 4.0 x 10-4 
 Hydroxylamine
 HONH2 
 HONH3+  
 1.1 x 10-8 
 Hydrazine
H2NNH2 
H2NNH3+  
 3.0 x 10-6 
 Aniline
 C6H5NH2 
 C6H5NH3+  
 3.8 x 10-10 
 Pyridine
 C5H5N 
 C5H5NH+  
 1.7 x 10-9 

6. Reaction of Weak Bases with Water
The generic reaction for a base reacting with water, producing its conjugate acid and hydroxide ion:
B + H2O  BH+ + OH-
(Yes, all weak bases do this – DO NOT
endeavor to make this complicated!)

7. A Weak Base Equilibrium Problem
What is the pH of a 0.50 M solution of ammonia, NH3, Kb = 1.8 x 10-5 ?
Step #1: Write the equation for the reaction
NH3 + H2O  NH4+ + OH-

8. A Weak Base Equilibrium Problem
What is the pH of a 0.50 M solution of ammonia, NH3, Kb = 1.8 x 10-5 ?
Step #2: ICE it!
NH3 + H2O  NH4+ + OH- I C E
0.50
- x +x +x x x x

9. A Weak Base Equilibrium Problem
What is the pH of a 0.50 M solution of ammonia, NH3, Kb = 1.8 x 10-5 ?
Step #3: Set up the law of mass action
NH3 + H2O  NH4+ + OH- E x x x

10. A Weak Base Equilibrium Problem
What is the pH of a 0.50 M solution of ammonia, NH3, Kb = 1.8 x 10-5 ?
Step #4: Solve for x, which is also [OH-]
NH3 + H2O  NH4+ + OH- E x x x
[OH-] = 3.0 x 10-3 M

11. A Weak Base Equilibrium Problem
What is the pH of a 0.50 M solution of ammonia, NH3, Kb = 1.8 x 10-5 ?
Step #5: Convert [OH-] to pH
NH3 + H2O  NH4+ + OH- E x x x

12. Soft cover book Pg

13. Text Pg do question 16.75
Then you can practice for hw 16.76

14. For conjugate acid base pairs only
Ka x Kb = Kw
pKa = -logKa
pKb = -logKb
pKa + pKb = 14
Now do question on Pg. 713

15. Hydrolysis of Salts Salt of strong acid and strong base – neutral
Salt of weak acid and strong base – basic
Salt of strong base and weak acid – acidic
In general Ka>Kb acidic
Kb>Ka basic
Soft cover book Pg. 387

16. Text Pg. 697
Text pg. 698 sample and 16.19

17. Reactions of Anions with Water
Anions are bases.
As such, they can react with water in a hydrolysis reaction to form OH− and the conjugate acid:
X−(aq) + H2O(l)
HX(aq) + OH−(aq)

18. Reactions of Cations with Water
Cations with acidic protons (like NH4+) will lower the pH of a solution.
Most metal cations that are hydrated in solution also lower the pH of the solution.

19. Reactions of Cations with Water
Attraction between nonbonding electrons on oxygen and the metal causes a shift of the electron density in water.
This makes the O-H bond more polar and the water more acidic.
Greater charge and smaller size make a cation more acidic.

20. Effect of Cations and Anions
An anion that is the conjugate base of a strong acid will not affect the pH.
An anion that is the conjugate base of a weak acid will increase the pH.
A cation that is the conjugate acid of a weak base will decrease the pH.

21. Effect of Cations and Anions
Cations of the strong Arrhenius bases will not affect the pH.
Other metal ions will cause a decrease in pH.
When a solution contains both the conjugate base of a weak acid and the conjugate acid of a weak base, the affect on pH depends on the Ka and Kb values.

22. Factors Affecting Acid Strength
The more polar the H-X bond and/or the weaker the H-X bond, the more acidic the compound.
Acidity increases from left to right across a row and from top to bottom down a group.

23. Factors Affecting Acid Strength
In oxyacids, in which an OH is bonded to another atom, Y, the more electronegative Y is, the more acidic the acid.

24. Factors Affecting Acid Strength
For a series of oxyacids, acidity increases with the number of oxygens.

25. Factors Affecting Acid Strength
Resonance in the conjugate bases of carboxylic acids stabilizes the base and makes the conjugate acid more acidic.

26. Lewis Acids Lewis acids are defined as electron-pair acceptors.
Atoms with an empty valence orbital can be Lewis acids.

27. Lewis Bases Lewis bases are defined as electron-pair donors.
Anything that could be a Brønsted–Lowry base is a Lewis base.
Lewis bases can interact with things other than protons, however.

28. Soft covered book Pg. 288
Example and practice