Henry's Law
Calculate how much gas dissolves in a liquid based on pressure.
Explains carbonation, scuba diving, and blood gases.
The Formula
C = k_H × P
Henry's law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid. Higher pressure forces more gas into solution.
Variables
| Symbol | Meaning |
|---|---|
| C | Concentration of dissolved gas (mol/L) |
| k_H | Henry's law constant (mol/L/atm, specific to each gas and temperature) |
| P | Partial pressure of the gas above the liquid (atm) |
Example 1
CO₂ has k_H = 0.034 mol/L/atm at 25°C. Find dissolved CO₂ at 2 atm pressure.
C = 0.034 × 2
C = 0.068 mol/L
Example 2
O₂ has k_H = 0.0013 mol/L/atm. How much dissolves at sea level (P_O₂ = 0.21 atm)?
C = 0.0013 × 0.21
C = 0.000273 mol/L ≈ 2.73 × 10⁻⁴ mol/L
When to Use It
Use Henry's law when:
- Calculating gas solubility in beverages (carbonation)
- Understanding decompression sickness in scuba diving
- Modeling oxygen and CO₂ exchange in blood
- Designing gas absorption equipment in industry