The solubility of oxygen in pure water at 25 °C and 1.0 atm pressure is approximately 1.22 × 10−3 mol dm−3.
Understanding the solubility of oxygen is crucial in many fields, from environmental science and aquatic life support to industrial processes. Oxygen solubility refers to the maximum amount of gaseous oxygen that can dissolve in a given amount of solvent, typically water, under specific conditions.
It's important to note that the solubility of oxygen is not a single, fixed number; it varies depending on several factors, including temperature, pressure, and the presence of other dissolved substances (like salts). Therefore, specifying the conditions is essential when discussing oxygen solubility.
Oxygen Solubility in Pure Water (Reference Data)
According to the provided reference, the solubility of oxygen in pure or fresh water under specific conditions is as follows:
| Condition | Solubility (mol dm−3) | Notes |
|---|---|---|
| Pure or Fresh Water | About 1.22 × 10−3 | At 25 °C and 1.0 atm of O₂ pressure |
| Pure or Fresh Water (Literature) | 1.18 to 1.25 × 10−3 | Range reported in different literature at 25 °C and 1.0 atm O₂ |
Based directly on the reference:
- At 25 °C and 1.0 atm of O₂ pressure in pure or fresh water, the solubility of oxygen is stated to be about 1.22 × 10−3 mol dm−3.
- The reference also notes that values reported in different literature sources for these conditions vary, ranging from 1.18 to 1.25 mol dm−3.
Factors Affecting Oxygen Solubility
While the reference provides a specific value for pure water at a standard temperature and pressure, in real-world scenarios, other factors influence how much oxygen dissolves:
- Temperature: As temperature increases, the solubility of gases, including oxygen, generally decreases. Colder water can hold more dissolved oxygen than warmer water.
- Pressure: Higher partial pressure of oxygen above the water surface leads to increased solubility (Henry's Law). The value given in the reference is for 1.0 atm of O₂ pressure.
- Salinity: The presence of dissolved salts decreases oxygen solubility. Oxygen is less soluble in saltwater than in freshwater.
Understanding these variables helps explain why dissolved oxygen levels in natural waters can vary significantly.
