1. Review:
H3PO4 is a polyprotic acid, meaning it has multiple protons to donate when dissociating with water.
a. Write Bronsted-Lowry reactions for the 3 successive removals or protons from this acid.
a. Which species in the reactions are amphoteric?
b. What is the conjugate base in the 2nd reaction?
c. What is the equation for the net process after all 3 removals? Hint: cross off intermediates
d. If the pH of a H3PO4 solution is 5.37, what is the [OH-]?

2. Objectives:
Understand the difference between a strong and weak acid and/or base.
Define acid and base dissociation constants and understand what they indicate.

3. Strong/Weak Acids and Bases
Strong acid or base DOES NOT mean more dangerous or more reactive!!! Hydrofluoric is a great example.
HF and glass
Breaking Bad Bathtub Scene

5. ↔

8. Day 2

9. Strong/Weak Acids and Bases What are strong acids and bases???
HA (aq) H2O (l) 
H3O+ (aq) A- (aq)
(Strong)
100% of the HA originally added will react
100% dissociation
React to completion
These are NOT equilibrium processes
The same is true for bases that are strong

10. Strong/Weak Acids and Bases What are strong acids and bases???
HA (aq) H2O (l) 
H3O+ (aq) A- (aq)
(Strong)
These are NOT equilibrium processes
Ka = acid dissociation constant =
K values will be simply listed as “large” for any acid or base that is strong

11. Strong/Weak Acids and Bases What are strong acids and bases???
HA (aq) H2O (l) 
H3O+ (aq) A- (aq)
(Strong)
Complete dissociation
Relative amounts
Before rxn
After rxn

12. Strong/Weak Acids and Bases

13. Strong/Weak Acids and Bases What are weak acids and bases???
HA (aq) + H2O (l) ↔
A- (aq) H3O+ (aq)
(Weak)
Only some of HA originally added will react
Partial (less than 100%) dissociation
React partially
These ARE equilibrium processes
The same is true for bases that are weak

14. Strong/Weak Acids and Bases What are weak acids and bases???
HA (aq) + H2O (l) ↔
A- (aq) H3O+ (aq)
(Weak)
These ARE equilibrium processes
Ka =
Most acids and bases considered weak are reactant favored and have Ka and Kb values < 1

15. Strong/Weak Acids and Bases What are weak acids and bases???
HA (aq) + H2O (l) ↔
A- (aq) H3O+ (aq)
(Weak)
Partial dissociation
Relative amounts
Before rxn
After rxn

16. Strong/Weak Acids and Bases

17. Strong/Weak Acids and Bases
The Big Idea:
The stronger the acid/base, the more product-favored, the larger the Ka/Kb value

18. This chart shows some common acids, ranked by strength, and compared to the each acid’s conjugate base

19. Try and answer the Final Connections questions on the handout
Try and answer the Final Connections questions on the handout. Pay special attention to 4 and 6!

20. 1. Which acid is stronger: sulfuric acid or sulfurous acid?

21. 2. Which base is stronger: the nitrite ion or the sulfite ion?

22. 3. Which of the acids from problem 1 has the stronger conjugate base?

23. 4. What is the relationship between the strength of an acid and it’s conjugate base?
Strong acids have weak conjugate bases

24. 5. Which acid is stronger: phosphoric acid, dihydrogen phosphate or hydrogen phosphate?

25. 6. How does the strength of an acid change as successive hydrogen ions are removed?
Acids get weaker as hydrogen ions are removed

27. Which acid would have the higher acid dissociation constant: HCl or HClO?
Which acid is the stronger acid: HBr or HBrO3?
Which base is stronger: the fluoride ion or the chloride ion?
1.0 M solutions of which acid would produce the greater H3O+ concentration in solution: hydroiodic acid or propanoic acid?
1.0 M solutions of which base would produce the greater OH-1 concentration in solution: the bromide ion or the nitrite ion?
Which acid is stronger: H2CO3 or HCO3-1?