1. DO NOW... HINT...if log (x) = y, then x = 10y
1) If log (109) = 9, what is log (100) equal to?
2) If log (Q) = 3, what is Q equal to?
HINT...if log (x) = y, then x = 10y

2. Richter Scale - Earthquakes6 5 7
Area Radius Richter Scale Diameter pH [H+]
mm M M M M M M M . 4 3 2 1

3. radius = 112.8 cm radius = 35.7 cm radius = 11.3 cm radius = 3.6 cm
pH = 2
pH = 3
pH = 1
Area Radius Richter Scale Diameter pH
mm 1 .
pH =

4. The pH scale is a way of expressing the strength of acids and bases
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+ (or OH-) ion. Under 7 = acid = neutral Over 7 = base

5. pH of Common Substances

7. pH of Common Substance More basic More acidic 14 1 x 10-14 1 x 10-0 0
pH [H1+] [OH1-] pOH
14 1 x x
13 1 x x
12 1 x x
11 1 x x
10 1 x x
9 1 x x
8 1 x x
6 1 x x
5 1 x x
4 1 x x
3 1 x x
2 1 x x
1 1 x x
0 1 x x
NaOH, 0.1 M
Household bleach
Household ammonia
Lime water
Milk of magnesia
Borax
Baking soda
Egg white, seawater
Human blood, tears
Milk
Saliva
Rain
Black coffee
Banana
Tomatoes
Wine
Cola, vinegar
Lemon juice
Gastric juice
More basic
7 1 x x
More acidic

8. (Remember that the [ ] mean Molarity)
Calculating the pH
pH = - log [H+]
(Remember that the [ ] mean Molarity)
Example: If [H+] = 1 X pH = - log 1 X 10-10
pH = - (- 10)
pH = 10
Example: If [H+] = 1.8 X 10-5 pH = - log 1.8 X 10-5
pH = - (- 4.74)
pH = 4.74

9. Try These! Find the pH of these:
A 0.15 M solution of Hydrochloric acid
2) A 3.00 X 10-7 M solution of Nitric acid

10. pH calculations – Solving for H3O+
If the pH of Coke is 3.12, [H3O+] = ???
Because pH = - log [H3O+] then
- pH = log [H3O+]
Take antilog (10x) of both sides and get
10-pH = [H3O+]
[H+] = = 7.6 x 10-4 M
*** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button

11. pH calculations Solving for H3O+
A solution has a pH of What is the Molarity of hydrogen ions in the solution?

12. pH Calculations pH = -log[H3O+] 10-pH = [H3O+] pOH = -log[OH-]
pH + pOH = 14
[H3O+] [OH-] = 1 x10-14
The pH scale is a concise way of describing the H3O+ concentration and the acidity or basicity of a solution
• pH and H+ concentration are related as follows:
pH = –log10[H+] or [H+] = 10–pH
• pH of a neutral solution ([H3O+] = 1.00 x 10–7 M) is 7.00
• pH of an acidic solution is < 7, corresponding to [H3O+] > 1.00 x 10–7
• pH of a basic solution is > 7, corresponding to [H3O+] < 1.00 x 10–7
• The pH scale is logarithmic, so a pH difference of 1 between two solutions corresponds to a difference of a factor of 10 in their hydronium ion concentrations
There is an analogous pOH scale to describe the hydroxide ion concentration of a solution; pOH and [OH–] are related as follows:
pH = –log10[OH–] or [OH–] = 10–pOH
• A neutral solution has [OH–] = 1.00 x 10–7, so the pOH of a neutral solution is 7.00
• The sum of the pH and the pOH for a neutral solution at 25ºC is = 14.00
pKw = –log Kw = –log([H3O+] [OH–]) =
(–log[H3O+]) + (–log[OH–]) = pH + pOH
• At any temperature, pH + pOH = pKw, and at 25ºC, where Kw = 1.01 x 10–14, pH + pOH = 14.00; pH of any neutral solution is just half the value of pKw at that temperature
pOH
pOH = -log[OH-]
[OH-]
10-pOH = [OH-]

13. Acid – Base Concentrations
pH = 3
pH = 11
10-1
H3O+
OH-
pH = 7
10-7
concentration (moles/L)‏
H3O+
OH-
OH-
H3O+
10-14
[H3O+] > [OH-]
[H3O+] = [OH-]
[H3O+] < [OH-]
acidic
solution
neutral
solution
basic
solution
Timberlake, Chemistry 7th Edition, page 332

14. PRACTICE pH & pOH PROBLEMS
[ H3O+]
(M)
pOH
[ OH– ]
ACID or BASE?
3.78 ?
3.89 x 10–4
5.19
1.00 x 10-7
1.66x10-4
10.22
6.03 x 10-11
ACID
3.41
10.59
2.57 x 10-11
ACID
1.55 x 10-9
6.46 x 10-6
BASE
8.81
7.00
1.00 x 10-7
7.00
NEUTRAL