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ChemistryEdu Logo Solution | Solubility of Gas in Liquid#

Solubility of Gas in Liquid#

  • All gases are soluble in all liquids to some extent depending on pressure.
  • For example, presence of carbon dioxide in cold drinks, presence of oxygen in blood, presence of oxygen in water.
  • Hydrogen chloride(HCl) gas is highly soluble in water.

Factors affecting the solubility of gases in liquids#

1. Nature of gas:#

  • Easily liquifiable gases(CO2, SO2, NH3) are more soluble in common solvents like water as compared to other gases(H2, N2).
  • The gases which can form hydrogen bonds or some other types of attractions with the solvent have higher solubility. Example: NH3 in H2O

2. Temperature:#

  • The solubility of gases in liquid decreases with increase in temperature because on increasing temperature, gas expands and its kinetic energy increases. Also for hydrogen bonded gases like NH3, H-bonds dissociate on increasing temperature.
  • Cold drinks are kept at low temperature to prevent the escape of CO2 gas.

3. Pressure:#

  • The effect of pressure on solubility of gases can be explained by Henry's law.
  • Henry's law states that the partial pressure of a gas on the surface of solution is directly proportional to its mole fraction dissolved in the solution.
\[p ∝ Χ_{gas}\]
\[p = {K_H Χ_{gas}}\]

where, p = partial pressure of gas above the surface of solution

Χgas = Mole fraction of gas in the solution

KH = Henry's Constant (It is the characteristic of a gas)

  • Graph for Henry's law will be a straight line with slope = KH as shown below:

Henry's Law Graph

  • Higher is the value of KH, lower is the solubility of gas.

Applications of Henry's Law#

  • To increase the solubility of CO2 in soft drinks and soda water, the bottle is sealed under high pressure.

  • Scuba drivers use tanks filled with air diluted with helium (Helium is less soluble in blood). This is because when scuba drivers are under water, increased pressure increases the solubility of air in the blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life. To avoid this, air is diluted with helium in the tank.

  • The partial pressure of oxygen is less at higher altitudes as compared to ground level, which causes low concentration of oxygen in the blood causing weakness.