Dissociation Constant of Water
As a frequently used special case, the dissociation constant of water is often expressed as Kw:
The concentration of water is not included in the definition of Kw, for reasons described in the article equilibrium constant.
The value of Kw varies with temperature, as shown in the table below. This variation must be taken into account when making precise measurements of quantities such as pH.
| Water temperature | Kw / 10−14 | pKw |
|---|---|---|
| 0°C | 0.1 | 14.92 |
| 10°C | 0.3 | 14.52 |
| 18°C | 0.7 | 14.16 |
| 25°C | 1.2 | 13.92 |
| 30°C | 1.8 | 13.75 |
| 50°C | 8.0 | 13.10 |
| 60°C | 12.6 | 12.90 |
| 70°C | 21.2 | 12.67 |
| 80°C | 35 | 12.46 |
| 90°C | 53 | 12.28 |
| 100°C | 73 | 12.14 |
Read more about this topic: Dissociation Constant
Famous quotes containing the words constant and/or water:
“I should say that the most prominent scientific men of our country, and perhaps of this age, are either serving the arts and not pure science, or are performing faithful but quite subordinate labors in particular departments. They make no steady and systematic approaches to the central fact.... There is wanting constant and accurate observation with enough of theory to direct and discipline it. But, above all, there is wanting genius.”
—Henry David Thoreau (1817–1862)
“It is the work of a brave man surely, in whom there was no guile! He rounded this water with his hand, deepened and clarified it in his thought, and in his will bequeathed it to Concord. I see by its face that it is visited by the same reflection; and I can almost say, Walden, is it you?”
—Henry David Thoreau (1817–1862)