| Themes > Science > Chemistry > General Chemistry > Solution and Solubility > Solubility of Solutes and Aqueous Solutions > Henry's Law | |||||||||||
|
Gas solubility is always limited by the equilibrium between the gas and a saturated solution of the gas. The dissolved gas will always follow Henry's law. The concentration of dissolved gas depends on the partial pressure of the gas. The partial pressure controls the number of gas molecule collisions with the surface of the solution. If the partial pressure is doubled the number of collisions with the surface will double. The increased number of collisions produce more dissolved gas. |
|||||||||||
The dissolving process for gases is an equilibrium. The solubility of a gas depends directly on the gas pressure. The number of molecules leaving the gas phase to enter the solution equals the number of gas molecules leaving the solution. If the temperature stays constant increasing the pressure will increase the amount of dissolved gas.
The Henry's law constant "k" is different for every gas, temperature and solvent. The units on "k" depend on the units used for concentration and pressure. The value for k is the same for the same temperature, gas and solvent. This means the concentration to pressure ratio is the same when pressures change. The following equation can be used to relate pressure and concentration changes.  |
|
Example: |
|
Solution: |
|
|
|
P1 = 150 mm Hg--------------------------------------------- |
C1 = 0.44 g O2 /100 mL solution |
|
P2 = 56 mm Hg----------------------------------------------- |
C2 = ? |
|
|
|
|
|
C2 = 0.15 g O2 /100 mL solution |