Chapter 5 Flashcards
A solution may be classified according to….
The states in which the solute and solvent occur
Since three states of matter, gas, liquid and crystalline solid exist,…………of homogeneous mixtures of solute and solvent are possible.
Nine types
Types of pharmaceutical solution
1 - gases in liquids
2- liquids in liquids
3- solid in liquids
The solubility of a gas in a liquid is…..
The concentration of the dissolved gas when it is in equilibrium with some of the pure gas above the solution
The solubility of gases in liquids depends on the:
• Pressure
• Temperature
• Presence of salts
• Chemical reactions
Henry’s low states that…..
In a very dilute solution (unsaturated) at constant temperature, the concentration of dissolved gas is proportional to the partial pressure of the gas above the solution at equilibrium.
Partial pressure is…..
The hypothetical pressure of that gas if it alone occupied the volume of the mixture at the same temperature
The partial pressure of the gas is obtained by….
Subtracting the vapor pressure of the solvent from
the total pressure above the solution
Partial pressure= (Total pressure-vapor pressure)
Vapor pressure is….
the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system.
Total pressure of a gas mixture is……
the sum of the partial pressures of each individual gas in the mixture.
The effect of the pressure on the solubility of a gas is expressed by……..
Henry’s law
•C=kp
The solubility of a gas is increased as…..
the pressure of the gas increased, so that the gas escapes when the pressure above the solution is decreased.
This phenomenon is commonly recognized in effervescent solutions when the stopper of the container is removed.
( Henry’s law & soft drinks )
Soft drink contain…..
Carbonated water
Water with dissolved carbon dioxidegas
( Henry’s law & soft drinks )
The drinks are bottled with a…..
Co2 pressure greater than 1 atm
( Henry’s law & soft drinks )
When The bottle is opened…….
The pressure of CO2 decreases and the solubility of
CO2 also decreases , according to Henry’s law.
Therefore, bubbles of CO2 escape from solution.
As the temperature is increased the solubility of of most gases……
decreases, owing to the greater tendency of the gas to expand.
The pharmacist must be careful in opening containers of……
gaseous solutions in warm climates.
A vessel containing a gaseous solution or a liquid with high vapor pressure such as…….
Ethyl nitrate, should be immersed in ice or cold water for some time to reduce the temperature and pressure of the gas befor opening the container.
Gases are often liberated from solutions in which they are dissolved by the introduction of…..
An electrolyte such as NaCl and sometimes by a non - electrolyte such as sucrose
This phenomenon is known as salting-out
The salting out effect may be demonstrated by …..
adding a small amount of salt to a “carbonated“ solution.
(Salting - out)
The resultant escape of gas is due to
the attraction of the salt ions or the highly polar non electrolyte for the water molecules, which reduces the density of the aqueous environment adjacent to the gas molecules.
Henry’s law applies strictly to…..
gases which are slightly soluble in solution and which do not react with the solvent.
Gases such as ……………………… show deviations as a result of …………………………………
hydrogen chloride, ammonia and CO2
chemical reaction between the gas and solvent result in increasing the solubility.
Accordingly, hydrogen chloride is about 10,000 times more soluble in water than is oxygen.
