What is pH and pOH? How are they both related?
Key Points
- pH is logarithmic measurement of the hydrogen ion concentration in a solution.
- pH = -log10[H+]
- A pH change of 1 represents a 10 fold change in the hydrogen ion concentration.
- As the pH increases the hydrogen ion concentration [H+] decreases.
- As the pH increases the hydroxide ion concentration [OH-] increases.
- pOH is a logarithmic measurement of the hydroxide ion concentration in a solution.
- pOH = -log10[OH-]
- The concentration of hydrogen ions multiplied by the concentration of hydroxide ions in an aqueous solution is a constant.
- The dissociation constant for water is Kw = [H+] [OH-] = 1 x 10-14 at 25°C
- pH + pOH =14
pH and POH table
|
pH |
-1 |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
|
[H+] |
101 |
100 |
10-1 |
10-2 |
10-3 |
10-4 |
10-5 |
10-6 |
10-7 |
10-8 |
10-9 |
10-10 |
10-11 |
10-12 |
10-13 |
10-14 |
10-15 |
|
[OH-] |
10-15 |
10-14 |
10-13 |
10-12 |
10-11 |
10-10 |
10-9 |
10-8 |
10-7 |
10-6 |
10-5 |
10-4 |
10-3 |
10-2 |
10-1 |
100 |
101 |
|
pOH |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
-1 |
|
Kw |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |
10-14 |