Liquid Dosage Forms

Question 1

The amount of substance that passes into solution in order to establish this equilibrium at constant temperature and so produce a saturated solution is known as the

Answer 1

solubility of the substance

Question 2

Involves a phase change so that molecules of solid become
molecules of solute in the solvent in which the crystal is
dissolving.

Answer 2

Interfacial Tension

Question 3

Replacement of the crystal molecules by solvent molecules, which is determined by their relative affinity for each other and their ability to overcome the cohesive forces present.

Answer 3

Interfacial Reaction

Question 4

May be considered as a process of relocation of
solute molecules from an environment where they are
surrounded by other identical molecules

Answer 4

Dissolution

Question 5

In order for the process of dissolution to occur spontaneously at a constant pressure, the accompanying change in free energy or_____ must be _____

Answer 5

Gibbs free energy (ΔG); negative

Question 6

The rate of diffusion usually obeys _____. This states that the rate of change in concentration of dissolved material with time is directly proportional to the concentration difference between the two sides of the diffusion layer

Answer 6

Fick’s Law of Diffusion

Question 7

States that the rate of mass transfer of solute molecules or ions through a static diffusion layer is directly proportional to the area available for molecular or ionic migration, the concentration difference across the boundary layer, and is inversely proportional to the thickness of the boundary layer

Answer 7

Noyes-Whitney Equation

Question 8

pH changes leading to ____ may result in
precipitation.

the solubility of the unionized species is ___ than that of the ionized form

Answer 8

unionization; less

Question 9

Introduction of a _____ can produce a large improvement in water solubility as evidenced by the more than 100-fold difference in the solubility of phenol compared with benzene.

Answer 9

hydrophilic hydroxyl group

Question 10

Effective concentration of ions, which are ___ than the actual concentration since ions become ___ associated with other oppositely charged ions, and ____ effectively contribute to the system as completely allocated ions

Answer 10

lower; strongly; do not

Question 11

The solubility of non- electrolytes depends on the formation of _______ between their molecules and those of water

Answer 11

weak inter-molecular bonds (hydrogen
bonds)

Question 12

Many solutes dissociate into ions if the _____of the solvent is ___ enough to cause sufficient separation of the attractive forces between the oppositely charged ions.

Answer 12

dielectric constant; high

Question 13

The amount of strong acid or strong base, expressed as moles of H+ or OH− ion, required to change the pH of 1 liter of the buffer by 1 pH unit

Answer 13

Buffer Capacity

Question 14

States that at constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

Answer 14

Henry’s Law

Question 15

The solubility of most gases in liquids _____ as the temperature rises

Answer 15

decreases

Question 16

The presence of _____ may also decrease the solubility of a gas in water by a ____ process, which is caused by the marked attraction exerted between electrolyte and water

Answer 16

electrolytes; salting out

Question 16

The presence of _____ may also decrease the solubility of a gas in water by a ____ process, which is caused by the marked attraction exerted between electrolyte and water

Answer 16

electrolytes; salting out

Question 17

Usually dependent on temperature, as dictated by the ____, and are exhibited by positive or negative deviations from ____

Answer 17

Phase Rule (J. Willard Gibbs); Raoult’s Law

Question 18

States that the solute is distributed between the two liquids in such a way that the ratio of the activities of the substance in each liquid is a constant

Answer 18

Nernst Distribution Law

Question 19

Colloid or colloidal suspension with a particle size range of up to about _, and coarse dispersions with ____ particles

Answer 19

1 µm; larger

Question 20

Charges in the ____ are held tightly to the particle and this is therefore known as the fixed layer, whereas charges within the ____ are more mobile and can move away from the solid surface and hence this is denoted the ____

Answer 20

Inner layer; fixed layer
outer layer; diffuse layer

Question 21

Induced to prevent caking, which has a higher chance of occurring for small sized particles

Answer 21

Flocculation

Question 22

explains the aggregation of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium.

Answer 22

DLVO Theory

Question 23

generally desirable, as the particles will remain as loose floccules rather than becoming aggregated, and so it follows that addition of low to medium concentrations of ionic materials that will be beneficial for pharmaceutical suspension formulations.

Answer 23

Secondary Minimum Zone

Question 24

Reducing particle size will ___ diffusion and ___ sedimentation, with a larger effect on the sedimentation rate.

Answer 24

increase; reduce

Question 25

A ___sedimentation rate would be optimal, suggesting that a _____ system is more desirable; however, __- is key to ensuring that dosing from the suspension is reproducible, and so a ___ system would be better in this respect.

Answer 25

slow; deflocculated; reversibility; flocculated

Question 26

When two immiscible liquids are combined, they will
form distinct layers with a minimum area of contact _____ that also has a minimum surface free energy. As the particle size ____, the interfacial area _____, as well as the free energy. Hence, emulsions are ________, and droplets may try to _____ to counter this rise in free energy.

Answer 26

interfacial area; diminishes; increases; thermodynamically unstable; coalesce

Question 27

Is irreversible and is the fusing together of the oil droplets, which may eventually lead to breaking. This occurs when repulsive forces are lowered and droplets approach the primary minimum

Answer 27

Coalescence

Question 28

Is irreversible, and is due to sufficient solubility of the internal phase in the external phase, wherein smaller droplets may donate themselves to larger droplets. This occurs in emulsions with sub-micrometer droplets (less than ~600 nm), and differs from coalescence wherein there is no contact needed between the droplets.

Answer 28

Ostwald Ripening

Question 29

____ are important in o/w emulsions stabilized by ___ emulsifiers, whereas ____, which arise when hydrated polymer chains approach one another, dominate with ____ emulsifiers and in w/o emulsions.

Answer 29

Electrostatic repulsions; ionic; steric repulsive forces; non-ionic

Question 30

Used to reduce interfacial tension making droplets easier to break- up during mixing and reducing the tendency to recombine

Answer 30

Surfactants

Question 31

The ___ the HLB number, the more hydrophilic or water soluble the surfactant, and the ___ the number the more lipophilic or oil soluble the surfactant.

Answer 31

Higher; Lower

Question 31

The ___ the HLB number, the more hydrophilic or water soluble the surfactant, and the ___ the number the more lipophilic or oil soluble the surfactant.

Answer 31

Higher; Lower