Lec.10 Eman

Question 1

Which factor affects sedimentation by increasing particle size?
a) Temperature
b) Viscosity
c) Density difference
d) Brownian motion

Answer 1

a) Particle size

Question 2

What effect does an increase in viscosity have on sedimentation?
a) Decreases sedimentation
b) Increases sedimentation
c) No effect on sedimentation
d) Promotes mixing instead of sedimentation

Answer 2

b) Increases sedimentation

Question 3

What is the lower size limit of particles that obey Stokes’s equation when subjected only to the force of gravity?
a) 0.1 um
b) 0.5 um
c) 1 um
d) 5 um

Answer 3

b) 0.5 um

Question 4

What instrument can be used to produce a force one million times that of gravity to bring about sedimentation in colloidal particles?
a) Ultrasonic bath
b) Centrifuge
c) Ultracentrifuge
d) Magnetic stirrer

Answer 4

c) Ultracentrifuge

Question 5

What can viscosity study provide information about in a colloidal system?
a) Particle size distribution
b) Surface charge of particles
c) Molecular weight of the dispersion medium
d) Shape of particles in dispersion

Answer 5

d) Shape of particles in dispersion

Question 6

How does the shape of particles in a colloidal dispersion affect viscosity?
a) Spherocolloids form dispersions of higher viscosity
b) Linear particles form dispersions of higher viscosity
c) Spherocolloids form dispersions of lower viscosity
d) Linear particles form dispersions of lower viscosity

Answer 6

c) Spherocolloids form dispersions of lower viscosity

Question 7

What does the viscosity of a dispersion containing linear particles indicate about the solvation of the particles?
a) High solvation of the particles
b) Low solvation of the particles
c) No relationship to particle solvation
d) Indeterminate

Answer 7

b) Low solvation of the particles

Question 8

How does a linear colloid behave in a solvent with low affinity?
a) It assumes a spherical shape and viscosity increases
b) It assumes a spherical shape and viscosity decreases
c) It maintains its linear shape and viscosity increases
d) It maintains its linear shape and viscosity decreases

Answer 8

b) It assumes a spherical shape and viscosity decreases

Question 9

What can changes in viscosity indicate about the shape of flexible colloidal particles and macromolecules?
a) Changes in charge distribution
b) Changes in particle size
c) Changes in molecular weight
d) Changes in shape

Answer 9

d) Changes in shape

Question 10

Which scientist developed an equation of flow applicable to dilute colloidal dispersions of spherical particles?
a) Newton
b) Einstein
c) Boyle
d) Faraday

Answer 10

b) Einstein

Question 11

What is electrically induced motion in colloidal systems?
a) Movement of particles due to gravitational force
b) Movement of particles caused by thermal energy
c) Movement of charged surfaces in relation to a liquid phase
d) Movement of particles due to Brownian motion

Answer 11

c) Movement of charged surfaces in relation to a liquid phase

Question 12

What is one of the important applications of electrically induced motion?
a) Osmosis
b) Diffusion
c) Electrophoresis
d) Sedimentation

Answer 12

c) Electrophoresis

Question 13

What is electrophoresis?
a) Movement of particles under the influence of an electric field
b) Movement of particles due to concentration gradient
c) Movement of particles due to viscosity
d) Movement of particles due to osmotic pressure

Answer 13

a) Movement of particles under the influence of an electric field

Question 14

What is the driving force for electrophoresis?
a) Gravitational force
b) Thermal energy
c) Magnetic field
d) Electric field

Answer 14

d) Electric field