1. Catalyst

2. Cool Acid/Base Reaction

3. Lecture 7.5 – Acid/Base Titrations

4. Today’s Learning Targets
LT 7.12 – I can interpret the titration curve for strong acid/base titration and I can calculate the equivalence point and unknown concentrations from titration data.

5. Acid/Base Indicators
Indicators – Compounds that change color depending on pH.
Therefore, these compounds tell us the general pH of our solution based their color

6. Titrations Often, we have solutions of unknown concentrations
Titration – The controlled addition of solution of known concentration/volume to a solution of known volume, but unknown concentration.
Standard Solution – Solution whose concentration and volume with know precisely

7. Acid/Base of known volume and concentration.
Acid/Base of known volume and unknown concentration with an indicator.
Print out and paste in notes

8. Strong Acid Titrated with Strong Base
Walk students through what this graph means and label points on the graph

9. Strong Base Titrated with Strong Acid
Walk students through what this graph means and label points on the graph

10. Equivalence Point
Equivalence Point – The point at which the two solutions used in a titration are present in equal amounts.
We use indicators to spot this point
For strong acid/strong base titrations, it occurs at pH = 7
Moles of acid = moles of base at this point

11. Calculating Concentration for Strong Acid/Strong Base Titrations
Volume of base that was added in titration
Molarity of base
Mole Ratio from balanced chemical reaction
Volume of unknown acid

12. Class Example
If it takes 54 mL of 0.1 M NaOH to neutralize 12.5m L of an HCl solution, what is the concentration of the HCl?

13. Table Talk
If it takes 14.0 mL of M KOH to neutralize L of an HNO3 solution, what is the concentration of the HNO3?

14. Stop and Jot
It takes mL of 1.1 M HBr to neutralize L of an KOH solution, what is the concentration of the HBr?

15. Weak Acid Titrated with Strong Base
When titrating a weak acid or base with a strong acid or base, the titration curve looks different.
Equivalence point does not occur at pH = 7
More on the calculations associated with these next week!

16. Weak Acid Titrated with Strong Base

17. Weak Base Titrated with Strong Acid

18. Fill in the Box
In the grid provided, complete the 9 questions that are around the room.
Complete as many problems as possible.

19. What is the pH of this base?

20. Lecture 7.6 – Weak Acid/Base Equilibrium

21. Today’s Learning Targets
LT 7.14 – I can explain the autoionization of water and utilize this definition to explain the Kw equation.
LT 7.15 – I can write the acid and base dissociation constants for a given weak acid or base.

22. Woops! I Lied Again 
In an aqueous solution, there is no such thing as H+
H+ reacts with water to make the hydronium ion, H3O+:
H+ + H2O  H3O+
Therefore when we say [H+], we mean [H3O+]. You can use either in this class

23. Autoionization of Water
Water can act as either an acid or a base. It is amphoteric, it can function as either an acid or a base.
Therefore, in a solution of water, we have the equilibrium of:
H2O (l) + H2O (l) H3O+ (aq) + OH- (aq)
We can calculate the equilibrium constant of this reaction to be:
This is a powerful equation because it allows us to interconvert, so it is appreviated as Kw: ⇌

24. Where pH comes from… We now know that:
Therefore we can do the following:

25. Class Example
Calculate the [H+] in a solution of [OH-] = M. Calculate the pH of the solution.

26. Table Talk
Calculate the [OH-] in a solution of [H+] = 2 x 10-6 M. Calculate the pH of the solution.

27. Weak acids/Ka ⇌ Recall, a weak acid is partially dissociated.
Therefore, reactants and products are in equilibrium:
HA H+ + A-
The equilibrium constant can be written for all weak acids as:
The equilibrium constant for a weak acid equilibrium is known as the acid dissociation constant (Ka) ⇌

28. HF (aq) + H2O (l) H3O+ (aq) + F- (aq)
Class Example
You have a solution of the following acid:
HF (aq) + H2O (l) H3O+ (aq) + F- (aq)
Given that the equilibrium concentrations are [HF] = M, [H3O+ ] = 4.5 x 10-2 M, and [F- ] = 8.9 x 10-3 M, calculate the value of Ka. ⇌

29. HOC6H5 (aq) + H2O (l) H3O+ (aq) + OC6H5- (aq)
Table Talk
You have a solution of the following acid:
HOC6H5 (aq) + H2O (l) H3O+ (aq) + OC6H5- (aq)
Given that the equilibrium concentrations are [HOC6H5] = M, [H3O+ ] = 1.5 x 10-4 M, and [OC6H5- ] = 3.1 x M, calculate the value of Ka. ⇌

30. B (aq) + H2O (l) HB+ (aq) + OH- (aq)
Weak Bases/Kb
Just like with weak acids, a weak acid partially dissociates
Therefore, reactants and products are in equilibrium:
B (aq) + H2O (l) HB+ (aq) + OH- (aq)
The equilibrium constant can be written for all weak acids as:
The equilibrium constant for a weak base equilibrium is known as the base dissociation constant (Kb) ⇌

31. Relationship between Ka and Kb
Consider the weak acid, NH4+:
NH4+ (aq) NH3 (aq) + H+ (aq)
Additionally, consider the base in the above reaction:
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
The two equilibrium expressions can be written as: ⇌ ⇌
Have students write the two equilibrium expressions for this

32. Relationship between Ka and Kb
We can add the two equations together to obtain:
NH4+ (aq) NH3 (aq) + H+ (aq)
+ NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
H2O (l) H+ (aq) + OH- (aq)
When we add two equilibriums together, K is multiplied: ⇌ ⇌ ⇌
Have students multiply Ka by Kb

33. Class Example
Calculate the Kb for the fluoride ion (Ka = 6.8 x 10-4)

34. Table Talk
Calculate the Ka for the ammonium ion (Kb = 1.8 x 10-5)

35. White Board Problems

36. White Board Problems
1. You have a solution that has [H+] = M. What is the [OH-] for the solution? 2. Calculate the [H+] in a solution of [OH-] = M. Calculate the pH of the solution. 3. Write the acid dissociation constant for HF 4. Write the base dissociation constant for NH3 5. Write the acid dissociation constant for HCNO (the first H is acidic). 6. The Ka for benzoic acid is 6.3 x What is the value of the Kb for benzoic acid? 7. The Ka for nitrous acid is 4.5 x What is the value of the Kb for nitrous acid?

37. Exit Ticket
You titrate a strong acid with a strong base. Draw what the titration curve looks like in pH vs. Volume of Base Added graph.
You titrate 25.7 mL of of H2SO4with 67.8 mL of M of CsOH. What is the molarity of the H2SO4 that was titrated?
You measure the [H+] of a solution to be M. What is the pH? What is the [OH-]?
The Kb for pyridine (C5H5N) is 1.7 x What is the value of pyridine’s Ka?

39. Closing Time Read: 4.6 and 16 Homework:
Pre – Lab for Lab 12 due at start of class Monday/Tuesday