Rheological Properties of Pharmaceuticals

Question 1

Starch is __ as its viscosity increases with increase in shear stress

Answer 1

dilatant

Question 2

Bingham plastics follow Newton’s law of viscosity at low shears. T/F?

Answer 2

F. below yield value, behave as elastic solid; above yield value,behave as newtonian system

Question 3

Select which physical property is NOT rheological property

a) body and slip
b) spreadability
c) surface tension
d) viscosity

Answer 3

c) surface tension

Question 4

Rheology can be defined as

Answer 4

study of flow properties

Question 5

unit of kinematic viscosity is defined as

Answer 5

stoke

Question 6

Plastic flow is generally exhibited by

a) gellies
b) lotion
c) colloids
d) conc solid suspensions

Answer 6

d) conc solid suspensions

Question 7

Pseudoplastic flow is generally exhibited by

a) viscous pastes
b) sol of mucilages and gums
c) gellies
d) lotion

Answer 7

b) sol of mucilages(viscous secretion) and gums

Question 8

unit of relative viscosity is

Answer 8

dimensionless

Question 9

creep test is applied to evaluate the viscoelastic properties of what kind of formulation?

Answer 9

ointments

Question 10

deflocculated suspension with high conc of the dispersed solids exhibits the flow of type

a) dilatant
b) newtonian
c) plastic
d) pseudoplastic

Answer 10

a) dilatant

Question 11

unit of viscosity is defined as

Answer 11

poise

Question 12

In graph of shear stress(F) vs shear rate(G), what would happen if shearing is stopped?

Answer 12

stress in fluids fall immediately to 0(origin) when stop shearing

Question 13

A graph of viscosity vs shear rate, why the graph is horizontal?

Answer 13

1. viscosity is independent of shear rate

2. viscosity is constant with time

Question 14

diff btw kinematic viscosity and dynamic viscosity?

Answer 14

kinematic concerns with time taken to pour out, dynamic concerns with force used to make it flow

Question 15

Examples of non-newtonian fluid

Answer 15

plastic, pseudoplastic, dilatant

Question 16

What is dilatant flow?

Answer 16

opposite to pseudoplastic; viscosity increase with increase in shear rate

Question 17

To produce a stable suspension of solid particles,

Select one or more:

an electrolyte should be added.

a thickening agent should be added.

the concentration of dispersed phase must be very low.

the size of solid particles must be reduced.

Answer 17

a ththe size of solid particles must be reduced.ickening agent should be added.

Question 18

An oil-in-water emulsion

Select one or more:

contains particles of similar size.

is stabilised by surfactant adsorption on the surface of particles.

is stabilised by electrical repulsion between particles.

will show faster phase separation if viscosity is reduced.

Answer 18

is stabilised by surfactant adsorption on the surface of particles.

is stabilised by electrical repulsion between particles.

will show faster phase separation if viscosity is reduced.

Question 19

When solid particles in an aqueous medium are flocculated,

Select one:

the particles settle faster to the bottom.

viscosity decreases.

zeta potential increases.

shape of particle changes.

Answer 19

the particles settle faster to the bottom.

Question 20

According to the DLVO theory, irreversible particle aggregation can occur as a result of the thermal energy of the particles overcoming the following energy barrier:

Select one:

Primary maximum.

Secondary minimum.

Primary minimum.

Secondary maximum.

Answer 20

Primary maximum.