Final Exam (Lecture #02)

Question 1

Essential character common to all disperse systems?

Answer 1

large area to volume ratio

Question 2

Natural tendency of particles in dispersed system?

Answer 2

• come together and coalesce –> free energy will decrease if particles do this
• disperse systems tend to react spontaneously to decrease their free energy to a minimum
• therefore, disperse systems are unstable

Question 3

(2) ways to prevent sedimentation

Answer 3

1. add flocculating agent

2. add viscosity enhancers

Question 4

Loose networks of particles that do not form cakes and are easy to resuspend

Answer 4

flocks

Question 5

Kaolin-pectin oral suspension

Answer 5

Tx of diarrhea

Question 6

Electrostatic forces

Answer 6

repulsion forces

Question 7

Van der Waal’s forces or electromagnetic forces

Answer 7

attraction forces

Question 8

Born forces

Answer 8

short-range repulsive forces

Question 9

Forces due to changes in quantities of adsorbed solvent on the very close approach of neighboring particles

Answer 9

solvation forces

Question 10

Zig-zag motion for particles observed under microscope

Answer 10

Brownian motion

Question 11

Fick’s first law

Answer 11

diffusional properties

Question 12

Stoke’s law

Answer 12

sedimentation properties

Question 13

(2) ways to reduce rate of sedimentation

Answer 13

1. increase viscosity

2. increase density of solvent

Question 14

(2) main forces that must be controlled to stabilize suspensions

Answer 14

1. electrostatic forces

2. steric forces

Question 15

Fatty acid amine & gelatin

Answer 15

cationic adsorbents

Question 16

monobasic potassium phosphate

Answer 16

• anionic flocculant

- promotes flocculation

Question 17

Carboxy methylcellulose (CMC)
Carbopol-934
Veegum
Tragacant
Bentonite

Answer 17

• suspending agents

- increase viscosity

Question 18

minimum zeta potential that creates enough repulsion between particles to promote stability

Answer 18

25 mV

Question 19

Process where large particles grow at the expense of smaller particles due to differences in solubility

Answer 19

Ostwald ripening

Question 20

HPMC, Pluronic F68 & F127, Kollidon 30, SLS

Answer 20

viscosity increasing polymers and surfactants to prevent or slow Ostwald ripening

Question 21

Light laser doppler micro-electrophoresis

Answer 21

measures zeta potential

Question 22

Zeta Potential:
0 - 5 mV
30 - 50 mV
>50 mV

Answer 22

0 - 5 mV –> coagulation/flocculation
30 - 50 mV –> moderate/good stability
>50 mV –> excellent stability

Question 23

The study of the deformation and flow of matter under the influence of an applied stress

Answer 23

Rheology

Question 24

This non-Newtonian behavior is associated with increasing shear rate decreases viscosity

Answer 24

pseudoplastic

Question 25

This non-Newtonian behavior is associated with a “yield value”
-Examples: ketchup, hand creams, tooth paste

Answer 25

plastic flow –> you must apply a stress before they start flowing

Question 26

example of Newtonian flow

Answer 26

water –> no amount of shear stress will alter viscosity

Question 27

This non-Newtonian behavior is associated with increase shear rate increases viscosity
-Examples: nail polish

Answer 27

Dilatant flow –> resists flow as you apply more force

Question 28

Reversible, time-dependent decrease in viscosity at a constant shear rate

Answer 28

Thixotropy

Question 29

Why should an ideal suspending agent have a high viscosity at negligible shear (i.e. during shelf storage)?

Answer 29

to avoid settling

Question 30

Tragacanth, sodium alginate, carboxymethylcellulose, bentonite

Answer 30

pseudoplastic substances

Question 31

What type of suspension behavior does synovial fluid exhibit?

Answer 31

psuedoplastic –> warming up before exercise decreases viscosity and allows fluids to move easier between joints and protect

Question 32

Hyalgan (sodium hyaluronate)
Supartz (sodium hyaluronate)
Synvisc (Hylan G-F 20)
Orthovisc (high-MW hyaluronan)

Answer 32

Hyaluronan products for intra-articular injections