1. Acids and Bases
pH and pOH

2. Intro Quiz: Put these items in pH order from most acidic to least.
Blood
Milk
Water
Lemon juice
Baking soda
Coffee
Ammonia

3. Answer:
Lemon juice
Coffee
Milk
Water
Blood
Ammonia
Baking Soda

4. Defining & Using pH & pOH
Acid
neutral
Base pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Examples
1M HCl
0.1M HCl
Gastric juice ant venom
coca cola lemon juice vinegar
wine
coffee tomatoes
tap water saliva cow's milk
pure water
sea water
soap baking soda
detergents toothpaste
detergents washing soda
household cleaner
0.1M NaOH caustic oven cleaner
1M NaOH +
pOH
most acidic
<
----
-----
least acidic
least basic
>
most basic
=14

5. pH pH is a measure of the hydrogen ion concentration, [H+]
pH is calculated using the following formula: pH = -log10[H+]

6. pOH pOH is a measure of the hydroxide ion concentration, [OH-]
pOH is calculated using the following formula: pOH = -log10[OH-]

7. Solutions Acidic solution: When the [H+] is greater than [OH-]
Basic solution: When [OH-] is greater than [H+]
Basic solutions are also known as alkaline.

8. Indicators

9. Example 1: Find the pH of a 0.2mol L-1 (0.2M) solution of HCl
Calculate pH: pH = -log10[H+] pH = -log10[0.2] = 0.7

10. Example 2: Find the pOH of a 0.1mol L- (0.1M) solution of NaOH
Calculate pOH: pOH = -log10[OH-] pOH = -log10[0.1] = 1

11. Example 3: Find the pH of a 0.2 mol L-1 (0.2M) solution of H2SO4
Calculate pH: pH = -log10[H+] pH = -log10[0.4] = 0.4

12. Example 4: Find the pOH of a 0.1mol L-1 (0.1M) solution of Ba(OH)2
Calculate pOH: pOH = -log10[OH-] pH = -log10[0.2] = 0.7

13. pH + pOH = 14
And:
[H+] * [OH-] = 1 x 10-14

14. OR:
[H+]*[OH-] = Kw = 1 X 10-14
Take the -log of both sides of the equation
- log [H+] +(- log [OH- ]) = - log [1 X ]
pH + pOH = 14

15. About those H+’s Water molecules are highly polar
A water molecule that loses H+ becomes the negatively charge hydroxide ion OH-
The water molecule that gains a H+ (proton) becomes a hydronium ion, H30+
H2O (l) H3O+(aq) + OH-(aq)

17. Self Ionization
This is also known as the self ionization reaction of water
H2O (l) H3O+(aq) + OH-(aq)
This is because water is amphoteric.

18. Example (1):
Find the pH of a solution of sodium hydroxide that has a pOH of 2
pH = 14 - pOH
pH = = 12

19. Example (2): Find the [OH-] of a sulfuric acid solution with a pH of 3
Calculate the pOH
pOH = 14 - pH
pOH = = 11
Calculate [OH-] [OH-] = 10-pOH [OH-] = = mol L-1

20. Example pH [H+] [OH-] pOH 7 1.0 x 10-7M 1.0 x 10-7M 7
Etc.