Chapter 4

Question 1

Define a solution… –

Answer 1

mixture of two or more components that form a single phase, homogeneous down to the molecular or ionic level.

Question 2

Define a solvent….. -

Answer 2

a component that determines the phase of the solution constitutes the largest proportion of the system.

Question 3

Define a solute….. -

Answer 3

dispersed as molecules or ions throughout the solvent; i.e. dissolved in the solvent

Question 4

The solutes (whether gases, liquids or solids) are divided into two main classes;

Answer 4

• Non electrolytes
• Electrolytes.

Question 5

Define and give example of Non electrolytes solute …

Answer 5

Substances which do not yield ions when dissolved in water.

Example: sucrose, glycerin, naphthalene and urea.

Question 6

Define and give example of Electrolytes solute

Answer 6

• substances which form ions when dissolved in water (may be weak or strong).

• Example: HCl, Na sulfate, ephedrine & phenobarbital.

Question 7

Define solubility

Answer 7

the amount of solute that passes into solution when an equilibrium is established between the solution and excess, i.e. undissolved substance.

Concentration of solute in a saturated solution at a certain temperature.

Question 8

The transfer of molecules or ions from a solid state into solution is known as……

Answer 8

Dissolution

Question 9

According to the solubility of solute in solvent , solution may be:

Answer 9

• Saturated solution
• Unsaturated or sub-saturated
• Supersaturated solution

Question 10

Give three points of saturated solutions:

Answer 10

• The solution obtained when maximum amount of solute is dissolved in a solvent under given conditions.

• The solution in which the dissolved solute is in equilibrium with insoluble part (excess).

• Saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a precipitate.

Question 11

Define Unsaturated or sub-saturated solution

Answer 11

Solution containing dissolved solute in a concentration below that necessary for complete saturation at a definite temperature.

Question 12

Define Supersaturated solution

Answer 12

Solution containing dissolved solute in a concentration higher than that necessary for complete saturation at a definite temperature.

Question 13

Supersaturated solutions are prepared or result when…….

Answer 13

some condition of a saturated solution is changed, for example temperature, volume (as by evaporation), or pressure.

Question 14

Some salts such as …………. can be dissolved in large amounts at an elevated temperature and upon cooling…. –

Answer 14

Na thiosulfates and Na acetate

Fail to crystals from the solution

Question 15

Supersaturated solutions can be converted to stable saturated solutions……

Answer 15

• Seeding the solution with a crystal of solute.
• Vigorous agitation.
• Scratching the walls of the container.
• Addition of solvent.

Question 16

The solubility of a compound depends upon:

Answer 16

• The physical, Chemical properties of the solute and the solvent

• structural effects which lead to interactions between the solute and solvent

• the temperature, pressure and pH of the solution.

Question 17

1st rule of solubility

Answer 17

• like dissolves like
• Like polar drug and non polar one
• The property of being polar is polarity.