1. pH
What’s up the first letter lower case and the second letter capitalized?

2. Definition of pH
The pH of a substance is the negative log of the hydrogen ion concentration.
pH = - log[H+]
* The negative is used so the values turn out to be positive!

3. pH Scale
The pH scale is used to determine if the substance is acidic, neutral or basic.
0–1–2–3–4–5–6–7–8–9–10–11–12–13-14
Acidic neutral basic
The lower the pH, the more acidic it is.
The higher the pH, the more basic it is.

4. pH, what’s it all mean? p stands for the –log
H stands for the hydrogen ion
[ ] stands for the concentration in Molarity

5. How did it all begin?
Scientists found that water has a hydrogen ion concentration of 1 x 10-7M.
They needed a better, easier way to express this idea. Most people struggle with such small numbers.
1 x 10-7 = That’s small!!

6. Formula So let’s apply the formula: pH = -log[H+] pH = -log[1 x 10-7]

7. Do you see the pattern? If the [H+] = 1 x 10-5, the pH = 5
Whether you see the pattern or not, make sure you can use your calculator correctly.

8. Pick your answer and then click to find out.
What about this?
If the [H+] = 1 x 10-8, the pH = 8
If the [H+] = 1 x 10-9, the pH = 9
Then what is the pH if the [H+] = 2 x 10-9?
Pick your answer and then click to find out.

9. Correct! You are right, it is 8.7, between 8 and 9.
Check your work with your calculator:
pH = -log[2 x 10-9]
pH = 8.7

10. Interesting information about pH
Substance pH
Stomach acid 2
Soda 3
Grapes 4
Bread 5.5
Urine 6.6
Saliva 7
Blood 7.4
Eggs

11. Some common acids HCl is hydrochloric acid HNO3 is nitric acid
HC2H3O2 is acetic acid
H2CO3 is carbonic acid
H2SO4 is sulfuric acid
H3PO4 is phosphoric acid
H3C6H5O7 is citric acid