This document provides an overview of acid/base chemistry and pH. It defines pH as a measure of hydrogen ion concentration, describes the pH scale from 0-14, and explains how to calculate pH, pOH, and hydrogen or hydroxide ion concentration from other values. Sample problems demonstrate how to determine pH from concentration and vice versa, as well as the relationship between pH and pOH. Key points are that pH is a log scale measurement of acidity, and that the sum of pH and pOH equals 14 for any aqueous solution.

1. Acid/Base Chemistry
The pH scale and
what does it mean?
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2. pH
• What is it?
• What does it mean?
• How do you measure it?
• Can you determine other things
from pH?
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3. pH an Overview
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pH is the measure of the concentration of hydrogen
ions is a solution. pH is measured on a log scale.
pH = - log[H+]
pH is used to indicate the degree of acidity or
alkalinity (basic) of a solution.
A solution is of a water solvent (polar)
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4. 
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When there is a high [H+], the solution is acidic.
On the other hand when the [H+] concentration is
low, the solution is basic.
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So if there is a high [H+], there must be a low [OH-]
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If there is a low [H+], there must be a high [OH-]
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So what does H+ and OH- create?
H2O
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5. Water
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Pure water should have a neutral pH, due to have
equal amounts of [H+] & [OH-].
Acid and bases are created by adding polar
molecules to water to increase [H+], or increase
[OH-]
The pH scale is used to measure the acidity or
alkalinity of a solution.
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6. pH Scale
The pH scale ranges from 0 to 14. 0
being the most acidic and 14 being
the most basic.
Representative pH Values
Substance
pH
battery acid
0.5
gastric acid
1.5-2.0
lemon juice
2.4
cola
2.5
vinegar
2.9
orange juice
3.5
acid rain
4.5-5.0
tea
5.5
milk
6.5
pure water
7.0
saliva
7.0-7.4
blood
7.3-7.5
sea water
8.0
soap
9.0-10.0
ammonia
11.5
household bleach
12.5
lye (sodium hydroxide)
13.5
So what does the pH tell us about
[H+] of a solution?
If something has a pH of:
pH 1 = [H+] = 0.1 M
pH 2 = [H+] = 0.01 M
pH 3 = [H+] = 0.001M
pH 4 = [H+] = 0.0001M
pH 5 = [H+] = 0.00001M
pH 6 = [H+] = 1X 10-6M
pH 7 = [H+] = 1X 10-7M
pH 8 = [H+] = 1X 10-8M
pH 9 = [H+] = 1X 10-9M
pH 10=[H+] = 1X 10-10M
pH 11=[H+] = 1X 10-11M
pH 12=[H+] = 1X 10-12M
pH 13=[H+] = 1X 10-13M
pH 14=[H+] = 1X 10-14M
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7. How to Figure it out?
If you were given HCl with a concentration of 0.003M,
what would be the pH?
pH = -log [H+]
pH = -log[0.003M]
pH = 2.52
pH will not have a unit!!!
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8. How does pH and pOH relate?
pH and pOH relate in the following way
pH + pOH = 14
pOH is the measure of the [OH-], in a solution.
What would be the pOH of an solution with a pH of
5.75?
pOH = 14 - 5.75
pOH = 8.25
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9. If given pH
To determine the concentration from pH, one must do
the following:
[H+] = 10 (-pH)
antilog
So what is the [H+] of a solution with a pH of 12.05?
[H+] = 10 (-12.05)
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[H+] = MuhammadX 10 -13 M
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10. Sample Problem 1
What is the pH and pOH of an solution with [H+] of
3.33 X 10-9 M?
1st solve for pH
pH = -log [H+]
pH = - log[3.33 X 10-9 M]
pH = 8.48
2nd  solve for pOH
pOH = 14 – pH
pOH = 14 - 8.48
pOH = 5.52 (acidic)
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11. Sample Problem 2
What is the [H+] of a solution with a pOH of 4.14?
1st  determine pH
pH = 14 – pOH
pH = 14 – 4.14
pH = 9.86
2nd determine [H+]
(basic)
[H+] = 10 (-pH)
[H+] = 10 (-9.86)
[H+] = 1.38 X 10 -10 M
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12. Sample Problem 3
What is the pH of a solution with a [OH-] = 2.35 X 10 -9?
1st determine pOH
pOH = -log [OH-]
pOH = -log[2.35X10-9 M]
pOH = 8.63
2nd determine pH
pH = 14 – pOH
pH = 14- 8.63
pH = 5.37
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(acidic)
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13. Sample Problem 4
What is the pH of a solution that was made from 4.57g
of HCl dissolved in 750 mL of water?
1st  determine moles of HCl
4.57g HCl
1 mol HCl = 0.125 mol
HCl
36.46 g HCl
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14. Sample 4 ….
2nd determine concentration of [H+], since this is an
acid the [H+] would be the same as the concentration
of the whole molecule of HCl. We will get [H+] &
[Cl-], both with the total of 0.125 moles each.
So concentration will be moles / volume (L)
[H+] = 0.125 moles/ 0.750 L
[H+] = 0.333M
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15. Problem 4…
Next determine pH
pH = -log [H+]
pH = -log [0.333M]
pH = 0.48 (very acidic)
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16. Your Turn..
1. What is the [H+] of an acid with a pH of 5.56?
2. Determine the pH of a 0.0045 M HCl?
3. Determine pOH of a solution with a pH of 8.65?
4. What is the pH of a base with an [OH-] of
3.44X10-5 M?
Ans: 1. 1.35
2. 2.75X 10-6M
3. 5.35
4. 9.54
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