Gas Pressure and Solubility:
Liquids and solids exhibit practically no change of solubility
with changes in pressure. Gases as might be expected, increase
in solubility with an increase in pressure. Henry's Law states
that: The solubility of a gas in a liquid is directly proportional
to the pressure of that gas above the surface of the solution.
If the pressure is increased, the gas molecules are "forced"
solution since this will best relieve the pressure that has been
The number of gas molecules is decreased. The number of gas molecules
dissolved in solution has increased as shown in the graphic on
Carbonated beverages provide the best example of this phenomena.
All carbonated beverages are bottled under pressure to increase
the carbon dioxide dissolved in solution. When the bottle is
opened, the pressure above the solution decreases. As a result,
the solution effervesces and some of the carbon dioxide bubbles
|Quiz: Champagne continues to ferment
in the bottle. The fermentation produces CO2. Why
is the cork wired on a bottle of champagne?
Deep sea divers may experience a condition called the "bends"
if they do not readjust slowly to the lower pressure at the surface.
As a result of breathing compressed air and being subjected to
high pressures caused by water depth, the amount of nitrogen
dissolved in blood and other tissues increases. If the diver
returns to the surface too rapidly, the nitrogen forms bubbles
in the blood as it becomes less soluble due to a decrease in
pressure. The nitrogen bubbles can cause great pain and possibly
To alleviate this problem somewhat, artificial breathing mixtures
of oxygen and helium are used. Helium is only one-fifth as soluble
in blood as nitrogen. As a result, there is less dissolved gas
to form bubbles.
|Quiz: If a diver had the "bends",
describe how this can be treated.
Another application of Henry's Law is in the administration
of anesthetic gases. If the partial pressure of the anesthetic
gas is increased, the anesthetic solubility increases in the
|Quiz: The amount of dissolved oxygen
in a mountain lake at
10,000 ft and 50oF is __?_ than the amount of dissolved
oxygen in a lake near sea level at 50oF.
|A Coke at room temperature will have __?_ carbon
dioxide in the gas space above the liquid than an ice cold bottle.
| Hyperbaric therapy, which involves exposure
to oxygen at higher than atmospheric pressure may be used to
treat hypoxia (low oxygen supply in the tissues). Explain how
the treatment works.