Chapter 5

Question 1

A solution may be classified according to….

Answer 1

The states in which the solute and solvent occur

Question 2

Since three states of matter, gas, liquid and crystalline solid exist,…………of homogeneous mixtures of solute and solvent are possible.

Answer 2

Nine types

Question 3

Types of pharmaceutical solution

Answer 3

1 - gases in liquids
2- liquids in liquids
3- solid in liquids

Question 4

The solubility of a gas in a liquid is…..

Answer 4

The concentration of the dissolved gas when it is in equilibrium with some of the pure gas above the solution

Question 5

The solubility of gases in liquids depends on the:

Answer 5

• Pressure
• Temperature
• Presence of salts
• Chemical reactions

Question 6

Henry’s low states that…..

Answer 6

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.

Question 7

Partial pressure is…..

Answer 7

The hypothetical pressure of that gas if it alone occupied the volume of the mixture at the same temperature

Question 8

The partial pressure of the gas is obtained by….

Answer 8

Subtracting the vapor pressure of the solvent from
the total pressure above the solution

Partial pressure= (Total pressure-vapor pressure)

Question 9

Vapor pressure is….

Answer 9

the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system.

Question 10

Total pressure of a gas mixture is……

Answer 10

the sum of the partial pressures of each individual gas in the mixture.

Question 11

The effect of the pressure on the solubility of a gas is expressed by……..

Answer 11

Henry’s law
•C=kp

Question 12

The solubility of a gas is increased as…..

Answer 12

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.

Question 13

( Henry’s law & soft drinks )
Soft drink contain…..

Answer 13

Carbonated water
Water with dissolved carbon dioxidegas

Question 14

( Henry’s law & soft drinks )
The drinks are bottled with a…..

Answer 14

Co2 pressure greater than 1 atm

Question 15

( Henry’s law & soft drinks )
When The bottle is opened…….

Answer 15

The pressure of CO2 decreases and the solubility of
CO2 also decreases , according to Henry’s law.

Therefore, bubbles of CO2 escape from solution.

Question 16

As the temperature is increased the solubility of of most gases……

Answer 16

decreases, owing to the greater tendency of the gas to expand.

Question 17

The pharmacist must be careful in opening containers of……

Answer 17

gaseous solutions in warm climates.

Question 18

A vessel containing a gaseous solution or a liquid with high vapor pressure such as…….

Answer 18

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.

Question 19

Gases are often liberated from solutions in which they are dissolved by the introduction of…..

Answer 19

An electrolyte such as NaCl and sometimes by a non - electrolyte such as sucrose
This phenomenon is known as salting-out

Question 20

The salting out effect may be demonstrated by …..

Answer 20

adding a small amount of salt to a “carbonated“ solution.

Question 21

(Salting - out)

The resultant escape of gas is due to

Answer 21

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.

Question 22

Henry’s law applies strictly to…..

Answer 22

gases which are slightly soluble in solution and which do not react with the solvent.

Question 23

Gases such as ……………………… show deviations as a result of …………………………………

Answer 23

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.