Solubility of Gases in Liquids : Solubility of Gases in Liquids Factors affecting the Solubility of Gases in Liquids : Factors affecting the Solubility of Gases in Liquids The solubility of a gas in a liquid is the concentration of the dissolved gas when it is at equilibrium with some of the undissolved gas above the solution.
This solubility is dependant on
Chemical reactions, and
Micelles solubilization. Effect of Pressure : Effect of Pressure Deals with Henry's Law in that the concentration of dissolved gas is directly proportional to the partial pressure of the atmosphere at a constant temperature.
If pressure is increased then the solubility increases. C2 a P C2 = sP Slide 4: Solubility of Gases Pressure Solubility (g /100 g of H20) O2 N2 He Henry’s Law Slide 5: Applications
Preparation of carbonated beverages, beer, Champagne etc.
Determination of solubility of gases in liquid.
Henry’s law is strictly applicable, only when
When the temperature is maintained constant
When the gas does not involve in chemical reaction with the solvent
When the gas is slightly soluble in liquid Effect of Temperature : Effect of Temperature Increase in temperature decreases the solubility of the gases, This is due to
Ability of the gas to expand at higher temperatures
Increase in pressure at the elevated temperatures
Therefore the lower temperature is preferred for storage of these solutions.
Dissolved gases are removed by heating the solution
Distilled water for parenteral use is maintained at 80 0C.
Handling of solutions
One has to be very careful while handling the solutions of Ammonia, liquid bromine and chlorine Effect of the Presence of Salt : Effect of the Presence of Salt Gases are released from a liquid by an introduction of a salt. (Salting out)
This is due to greater affinity of the electrolytes towards the water molecules resulting in weakening of the gas solvent interactions.
Therefore if a salt is added then the solubility of the gas decreases. Effect of Chemical Reactions : Effect of Chemical Reactions The solubility of a gas will increase if the gas reacts with the solvent.
For these solutions Henry’s law is not applicable.
E.g. Ammonia and Carbon dioxide solutions.
Preparation of reagents such as Hydrochloric acid, sulphuric acid and nitric acid Effect of Micellar Solubilization : Effect of Micellar Solubilization Putting the gas molecules inside micelles increases the solubility of the gas. Micelles are used to increase the solubility of a non-polar solute (gas) in a polar solvent.
An example of this in the body is the lungs. The lungs allow the non-polar air to be transported through the polar water to the tissues. This is accomplished by a micellar transport system. Solubility of Liquids in Liquids : Solubility of Liquids in Liquids It is very common for two or more liquids to be mixed together in a pharmacy to make a solution, therefore the pharmacist needs to know what liquids can be mixed together without precipitation occurring. Miscibility of Liquids : Miscibility of Liquids Liquid-liquid systems are divided into two categories depending on the solubility of one substance in the other. The categories are complete miscibility and partial miscibility. Miscibility is the common solubilities of the components in liquid-liquid systems.
Complete miscibility is when the substances mix in all proportions. Examples of these are alcohol and water, alcohol and acetone, and benzene and carbon tetrachloride.
Partial miscibility is when the substances only mix partially. When mixed there are two layers formed each layer containing some of both liquids. Examples are phenol and water. The Influence of Foreign Substances on Solubility : The Influence of Foreign Substances on Solubility The influence of a foreign substance on a liquid-liquid system is similar to the idea of a three component system in the phase rule we studied earlier.
Remember that if the new substance is soluble in both of the other ones then they will all be soluble in each other. This is called blending.
An example of this is when succinic acid is added to the water-phenol mixture , succinic acid is soluble or completely miscible in each water and phenol therefore it causes a blending of the liquids making the mixture one phase. The Dielectric Constant and Solubility : The Dielectric Constant and Solubility As we have already discussed the dielectric constant of a substance effects the solubility of that substance.
If needed to see General Mechanisms of Solvent-Solute Interactions. It says that the polarity is dependent on the dielectric constant.
Also remember that LIKE DISSOLVES LIKE. This figure shows how the dielectric constant is related to solubility.