PHA 317 - Practical Test UPDATED ACTUAL Questions and CORRECT Answers
A suspension is a system in which a saturated insoluble solid (dispersed phase) is
heterogeneously dispersed in a liquid (continuous phase).
What is the difference between a An emulsion is a suspension made up of two liquids. One liquid is dispersed as fine
suspension, an emulsion and a solution? droplets (dispersed phase) in the other liquid (continuous phase).
A solution is the same as a suspension except the two components are
homogeneously dissolved.
Surfactants/Wetting Agents sit in the interphase between the solid and liquid,
reducing their interfacial tension.
How are suspensions stabilized?
Aside, all wetting agents are surfactants but not surfactants are wetting agents.
Stokes Law describes the sedimentation of the solid particles in a suspension.
ν = [2ga^2(ρ1 - ρ2)] ÷ [9η]
What is Stokes Law and what does it v = sedimentation rate
describe? g = gravity acceleration
a = radius of solid particles
ρ1 = density of dispersed phase
ρ2 = density of continuous phases
η = viscosity of the continuous phase
, Fine particles sediment slowly and can pack so
tightly to the point of caking that redispersion
Stokes' law shows that reducing the
becomes impossible.
particle size of the dispersed phase
reduces the sedimentation rate and
1. Keep particle size slightly higher to discourage
enhances the suspension stability.
caking.
Why is it an issue to reduce particle size
2. Flocculating agents (like surfactants) can sit in
too much?
the interphase allowing particles to form loose
How does one mitigate the issue?
clumps that can be redispersed instead of tight
packing that causes cakeing.
Electrolytes can be useful in producing a Electrolytes that are oppositely charged to the dispersed phase particles can act as
good suspension. flocculating agents. This produces a suspension that settles quickly and easily
resuspends (flocculated system)
What role do electrolytes play in the
formation of a good suspension? Adding too much will cover the particles like charges, making them repulsive to
Why is it an issue to add too much other particles. Any sedimentation that occurs will be slow and will cake. This is
electrolyte? called deflocculation.
In the Suspension Practical identify the Dispersed phase: Bismuth Subnitrate (common antacid)
compound that acted as the following: Continuous phase: Water
Suspension stabilizer: Bentonite
Dispersed phase Electrolyte: KH2PO4 (Monopotassium phosphate)
Continuous phase
Suspension stabilizer
Electrolyte
It would look like a parabolic curve. As the
concentration of electrolytes increases, initially it
In the Suspension Practical, what would the
would take fewer inversions to redisperse the
plot of
suspension, up to a point.
(Electrolyte Concentration) vs (Inversion for
redispersion) look like?
After this point, the number of inversions required
for redispersion will increase again.
Emulsions are usually defined by the O/W: Dispersed phase = oil, continuous phase = oil
dispersed and continuous phases. For the W/O: Dispersed phase = water, continuous phase = water
following emulsions, differentiate the O/W/O: Dispersed phase = O/W emulsion, continuous phase = oil
dispersed phase and continues phase. W/O/W: Dispersed phase = W/O emulsion, continuous phase = water
O/W emulsion
W/O emulsion
O/W/O emulsion
W/O/W emulsion
An emulsifying agent is usually a surfactant that occupies the interphase between
the two liquids.
How are emulsions stabilized?
It acts as a middleman, reducing the interfacial tension/energy and promoting the
formation and stabilization of an emulsion.
A suspension is a system in which a saturated insoluble solid (dispersed phase) is
heterogeneously dispersed in a liquid (continuous phase).
What is the difference between a An emulsion is a suspension made up of two liquids. One liquid is dispersed as fine
suspension, an emulsion and a solution? droplets (dispersed phase) in the other liquid (continuous phase).
A solution is the same as a suspension except the two components are
homogeneously dissolved.
Surfactants/Wetting Agents sit in the interphase between the solid and liquid,
reducing their interfacial tension.
How are suspensions stabilized?
Aside, all wetting agents are surfactants but not surfactants are wetting agents.
Stokes Law describes the sedimentation of the solid particles in a suspension.
ν = [2ga^2(ρ1 - ρ2)] ÷ [9η]
What is Stokes Law and what does it v = sedimentation rate
describe? g = gravity acceleration
a = radius of solid particles
ρ1 = density of dispersed phase
ρ2 = density of continuous phases
η = viscosity of the continuous phase
, Fine particles sediment slowly and can pack so
tightly to the point of caking that redispersion
Stokes' law shows that reducing the
becomes impossible.
particle size of the dispersed phase
reduces the sedimentation rate and
1. Keep particle size slightly higher to discourage
enhances the suspension stability.
caking.
Why is it an issue to reduce particle size
2. Flocculating agents (like surfactants) can sit in
too much?
the interphase allowing particles to form loose
How does one mitigate the issue?
clumps that can be redispersed instead of tight
packing that causes cakeing.
Electrolytes can be useful in producing a Electrolytes that are oppositely charged to the dispersed phase particles can act as
good suspension. flocculating agents. This produces a suspension that settles quickly and easily
resuspends (flocculated system)
What role do electrolytes play in the
formation of a good suspension? Adding too much will cover the particles like charges, making them repulsive to
Why is it an issue to add too much other particles. Any sedimentation that occurs will be slow and will cake. This is
electrolyte? called deflocculation.
In the Suspension Practical identify the Dispersed phase: Bismuth Subnitrate (common antacid)
compound that acted as the following: Continuous phase: Water
Suspension stabilizer: Bentonite
Dispersed phase Electrolyte: KH2PO4 (Monopotassium phosphate)
Continuous phase
Suspension stabilizer
Electrolyte
It would look like a parabolic curve. As the
concentration of electrolytes increases, initially it
In the Suspension Practical, what would the
would take fewer inversions to redisperse the
plot of
suspension, up to a point.
(Electrolyte Concentration) vs (Inversion for
redispersion) look like?
After this point, the number of inversions required
for redispersion will increase again.
Emulsions are usually defined by the O/W: Dispersed phase = oil, continuous phase = oil
dispersed and continuous phases. For the W/O: Dispersed phase = water, continuous phase = water
following emulsions, differentiate the O/W/O: Dispersed phase = O/W emulsion, continuous phase = oil
dispersed phase and continues phase. W/O/W: Dispersed phase = W/O emulsion, continuous phase = water
O/W emulsion
W/O emulsion
O/W/O emulsion
W/O/W emulsion
An emulsifying agent is usually a surfactant that occupies the interphase between
the two liquids.
How are emulsions stabilized?
It acts as a middleman, reducing the interfacial tension/energy and promoting the
formation and stabilization of an emulsion.
