1. Calculating pH (and pOH)

2. [H+] = the hydrogen ion concentrationpH
pH: “potential of hydrogen”
- A way of expressing the hydrogen ion concentration
pH = - log [H+]
[H+] = the hydrogen ion concentration

3. Calculating pH
Calculate the pH values using the equation pH = - log [H+]. Do you notice a pattern?
[H+] pH 1
1 x 10-3 M 2
1 x 10-5 M 3
1 x 10-7 M 4
1 x 10-9 M 5
1 x M
3.0
5.0
7.0
9.0
12.0

4. How do we calculate [H+] if we know the pH?
pH = - log [H+]
[H+] = the hydrogen ion concentration
[H+] = 10-pH

5. Calculating [H+]
Calculate the [H+] values using the equation [H+] = 10-pH. Do you notice a pattern? pH
[H+] 1
3.00 2
5.00 3
7.00 4
9.00 5
12.00
1 x 10-3 M
1 x 10-5 M
1 x 10-7 M
1 x 10-9 M
1 x M

6. Calculating pH pH [H+] Acidic Solution pH < 7.0 Neutral Solution
Basic Solution
pH > 7.0
[H+] > 1 x 10-7
[H+] = 1 x 10-7
[H+] < 1 x 10-7

7. The pH Scale - As pH increases, [H+] decreases
- As pH decreases, [H+] increases

8. [OH-] = the hydroxide ion concentration
pOH
pOH: “potential of hydroxide”
Just like pH:
- pOH is a convenient way of expressing the hydroxide ion concentration
pOH = - log [OH-]
[OH-] = the hydroxide ion concentration
Just like [H+]:
[OH-] = 10-pOH
pH + pOH = 14