1. Acids and Bases Chapter 19
Dr. Walker

2. Properties of Acids and Bases

3. Neutralization Reactions
HX MOH H2O MX

4. Organizer

5. Milk of Magnesia (antacid)
Common Bases
NaOH
Sodium Hydroxide
Lye
KOH
Potassium Hydroxide
Liquid Soaps
Mg(OH)2
Magnesium Hydroxide
Milk of Magnesia (antacid)
Al(OH)3
Aluminum Hydroxide
Maalox (antacid)

6. Common Acids

7. Common Acids

8. Defining Acids and Bases
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Defining Acids and Bases
Arrhenius Acid/Base
Arrhenius Acid: Increases H3O+ (aka H+, proton) concentration
HCl + H2O H3O+ + Cl-

9. Defining Acids and Bases
Write all
Defining Acids and Bases
Arrhenius Base: Increases OH- concentration
NaOH Na+ + OH-
Problem
Some bases don’t have OH-!

10. Defining Acids and Bases
Write all
Defining Acids and Bases
Bronsted-Lowry
Acids: Proton Donor
Bases: Proton Acceptor
Proton: Hydrogen atom that has lost it’s electron (H+)

11. Bronsted-Lowry
According to the Bronsted-Lowry definition, water acts as an acid because it gives up a proton!

12. Strong and Weak Acids/Bases

13. Strong and Weak Acids/Bases
Strong Acid – dissociates completely in solution
-Notice the HCl completely breaks apart
-Tends to be smaller molecules
Weak Acid – dissociates partially in solution
Notice the acetic acid stays mostly intact
-Tends to be larger, organic molecules

14. Electrolytes Solutions that can conduct electricity
Requires ions in solution (H+, Na+, Cl- , etc.)
Strong electrolytes
High ion content
Dissociate completely in solution (strong acids/bases)
Weak electrolytes
Lower ion content
Dissociate partially in solution (weak acids/bases)
Non-electrolytes
No dissocation, hence no ions in solution
Organic molecules

15. Amphoteric
Amphoteric – has properties of an acid and a base. Can act as either depending on situation
NH3 + H2O NH4+ + OH-
Water is the acid
H2O + HCl H3O+ + Cl-
Water is the base

16. Self-Ionization of Water
H2O H+ + OH-
This happens in every glass of water
This occurs in low enough concentration that it is not noticeable
[H+] = [OH-] = 1.0 x 10-7 M
[H+][OH-]= 1.0 x M

17. Concentration Concentration is expressed in Molarity (M = moles/liter)
Concentration is shown with [ ] brackets
0.1 = [HCl]
The HCl concentration is 0.1 M

18. The pH Scale pH = power of Hydrogen
pH measures hydrogen ion concentration
The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the molarity of the H+ ion.

19. The pH Scale
pH < 7
Acidic
pH = 7
Neutral
pH > 7
Basic

20. Calculating pH Works on powers of 10 Scientific Notation
Entering problems into the Calculator
Number
EE (Ti-30) or exp ($ 1/Casio)
Exponent
Solve by hitting “log”, “+/-”
Do not hit the multiply
button!!!!! It will mess you
up!

21. Calculating pH pH = - log [H3O+] Example: [H3O] = 1.0 x 10-5
Note: This number is a molarity (or concentration!!)
You’re given this most of the time, but you could have to calculate it!
log [1.0 x 10-5] = -5
-log [1.0 x 10-5] = 5
pH = 5

22. Other Examples
What is the pH of a 5.0 x 10-6 solution of sulfuric acid?
What is the pH of a 1.4 x solution of hydrochloric acid?
What is the pH of a solution of HCl containing 0.1 moles and 2.5 L total volume?

23. Other Examples
What is the pH of a 5.0 x 10-6 solution of sulfuric acid?
5.0, ee/exp, 6, (+/-)
Log, (+/-)
= 5.30
What is the pH of a 1.4 x solution of hydrochloric acid?
= 9.85
What is the pH of a solution of HCl containing 0.1 moles and 2.5 L total volume?
Find molarity, take – log of that
(-log [0.1/2.5]) = 1.40

24. Finding [H3O+] from pH [H3O+] = 10-pH
You can perform the reverse and determine [H3O+] from p
[H3O+] = 10-pH
What is the hydronium concentration of a solution with pH = 9.7 ?
[H3O+] =
[H3O+] = 1.99 x 10-10

25. Fighting the Calculator
What is the hydronium concentration of a solution with pH = 9.7 ?
[H3O+] = 10-pH
[H3O+] =
pH, (+/-), 2nd function, log
[H3O+] = 1.99 x 10-10

26. Examples
What is the hydronium concentration of a solution with pH = 11.2?
What is the hydronium concentration of a solution with pH = 1.9?

27. Examples
What is the hydronium concentration of a solution with pH = 11.2?
11.2, (+/-), 2nd function, log = 6.31 x 10-12
What is the hydronium concentration of a solution with pH = 1.9?
= or 1.3 x 10-2
Note: For decimals with only a few zeros, the calculator won’t convert to scientific notation for you.

28. pOH Measures Hydroxide (OH-) concentration pOH = -log [OH-]
pH + pOH = 14
What is the pOH of a solution with a pH = 6.7?
6.7 + pOH = 14
pOH = 7.3

29. pH Testing Blue litmus paper (red = acid)
There are several ways to test pH
Blue litmus paper (red = acid)
Red litmus paper (blue = basic)
pH paper (multi-colored)
pH meter (7 is neutral, <7 acid, >7 base)
Universal indicator (multi-colored)
Indicators like phenolphthalein
Natural indicators like red cabbage, radishes

30. pH Indicators
Indicators are dyes that can be added that will change color in the presence of an acid or base.
Some indicators only work in a specific range of pH
Once the drops are added, the sample is ruined
Some dyes are natural, like radish skin, red cabbage, and beets

31. Common Chemical Indicators

32. Indicators

33. Indicator Questions
What is the pH of solution if bromothymol blue turns blue and thymol blue turns yellow?
A) 5.5
B) 7.3
C) 7.8
D) 8.7

34. Indicator Questions Notice – bromothymol blue is blue above 7.6
Thymol blue is yellow below 8.0
The only choice that qualifies is
c) 7.8

36. Titrations
Titration: A method used to determine the unknown concentration of a substance in solution
A buret is used for this
Math involves a dilution calculation
Remember, M1V1 = M2V2

37. Titrations
Titrations use stoichiometry to determine endpoint of reactions (no I won’t make you do it)
Equivalence point
# moles acid = # moles base in a titration
If the proper indicator is chosen, the end point and equivalence point should be the same.

38. Titrations How could you tell when a titration is finished?
Take the pH at given volume points with pH paper
Indicators: you need to use an indicator that turns color when your titration is complete.
End Point: Point in a titration where a color change takes place

40. Skills To Master
Differentiating between acids and bases given specific properties
Calculating pH, [H+], and pOH given one of these values
Evaluating the proper indicator for a given pH range
Evaluating the pH given colorimetric results from indicators