PHA 317 practical test 2025 Questions
and Answers Top Rated A+
what is the flocculating agent in suspensions?
Trisodium citrate
-will prevent caking and allows easy redispersion
-increase in repulsion and particles aggregation with larger gaps
so they can be easily redispersed
what is the role of glycerin?
it attracts water as a wetting agent to prevent suspension from
drying out
what type of curve is formed from electrolyte conc vs
inversion dispersion?
parabolic curve
- at the conc of electrolyte increase it takes fewer inversions of
redispersion os suspension up to a point. after this point the
number of inversion for redispersion will increase
which formula was most stable and why?
formula C
- has suspending agent (bentonite) and flocculating agent
(trisodium citrate) in it
-increase in viscosity medium
which was the least stable and why?
formula A
- it has no Bentonite or flocculating agent
-will have rapid caking and sedimentation
what should the inversions be like?
gentle and not vigorous as you will get a frothy suspension which
is hard to inspect.
what is an emulsion?
an emulsion is a mixture of immiscible liquids where one is
dispersed on the continuous phase
what is a multi emulsion?
,emulsions with dispersed phase containing droplets of another
phase
-eg: w/o/w
-dispersed phase is w/o
-continous phase water
what are microemulsions?
spherical droplets around 5-40nm dispersed in another phase
using an emulsifier or mix of emulsifiers in high conc
why do we need to stabilise emulsion?
there is a large surface area between the 2 immiscible liquids that
have interfacial tension, which is thermodynamically unstable
how do we stabilise emulsions?
using an emulsifying agents like a surfactant
-will sit in the interphase between 2 immiscible liquids that is
going to reduce interfacial tension and promote stability
what does HLB stand for
hydrophilic-lipophilic balance
- numbers between 0-20
- it shows the affinity a surfactant has for water for oil
a larger HLB value shows what...
a more hydrophilic water loving
-best suited for oil in water emulsion o/w
a smaller HLB value shows what...
a more lipophilic water hating (oil loving) emulsion
-best suited for water in oil emulsion w/o
example of hydrophilic
detergent
expample of lipophilic
antifoaming
example of water dispersible
wetting agents
what is the HLB mix equation?
[ f a HLB a ] + [f b HLB b ]
- will determine the final HLB value of a mix of surfactants
why do we need stabilisers?
, to attempt to keep 2 immiscible liquids mixed
- to reduce the interfacial tension between the separated phases
what are the steps of emsulion breakdown? EFCCB
Emuslion
Floculation
Coalescence
Creaming
Breaking
what is used to increase continuous phase viscosity?
methycellouse
what happens when you increase continuous phase
viscosity
the viscosity increases so there will be a decrease in flocculation
or coalescence rate as droplets will struggle to move/ disperse
a reduce creaming ratio
what is the creaming ratio equation?
CR= volume creamed/ total vol of emulsion
what is liquid paraffin?
the emulsion formed
an oil in water emulsion
what is the appropriate HLB value for liquid paraffin?
- higher HLB value
- as it is more hydrophilic
- the more hydrophilic the more suited for an o/w emulsion
- between 8-16
what is was used to investigate the effect of continuous
phase viscosity?
- 0.5% methycellulose
-2% methylcellouse
which emulsion was more stable of the aqueous phase?
2% methylcellulose solution
why was the 2% methylcellulose more stable?
1) higher viscosity- reduces creaming process
2) reduced coalescence- as it is more viscous and hard for oil
and Answers Top Rated A+
what is the flocculating agent in suspensions?
Trisodium citrate
-will prevent caking and allows easy redispersion
-increase in repulsion and particles aggregation with larger gaps
so they can be easily redispersed
what is the role of glycerin?
it attracts water as a wetting agent to prevent suspension from
drying out
what type of curve is formed from electrolyte conc vs
inversion dispersion?
parabolic curve
- at the conc of electrolyte increase it takes fewer inversions of
redispersion os suspension up to a point. after this point the
number of inversion for redispersion will increase
which formula was most stable and why?
formula C
- has suspending agent (bentonite) and flocculating agent
(trisodium citrate) in it
-increase in viscosity medium
which was the least stable and why?
formula A
- it has no Bentonite or flocculating agent
-will have rapid caking and sedimentation
what should the inversions be like?
gentle and not vigorous as you will get a frothy suspension which
is hard to inspect.
what is an emulsion?
an emulsion is a mixture of immiscible liquids where one is
dispersed on the continuous phase
what is a multi emulsion?
,emulsions with dispersed phase containing droplets of another
phase
-eg: w/o/w
-dispersed phase is w/o
-continous phase water
what are microemulsions?
spherical droplets around 5-40nm dispersed in another phase
using an emulsifier or mix of emulsifiers in high conc
why do we need to stabilise emulsion?
there is a large surface area between the 2 immiscible liquids that
have interfacial tension, which is thermodynamically unstable
how do we stabilise emulsions?
using an emulsifying agents like a surfactant
-will sit in the interphase between 2 immiscible liquids that is
going to reduce interfacial tension and promote stability
what does HLB stand for
hydrophilic-lipophilic balance
- numbers between 0-20
- it shows the affinity a surfactant has for water for oil
a larger HLB value shows what...
a more hydrophilic water loving
-best suited for oil in water emulsion o/w
a smaller HLB value shows what...
a more lipophilic water hating (oil loving) emulsion
-best suited for water in oil emulsion w/o
example of hydrophilic
detergent
expample of lipophilic
antifoaming
example of water dispersible
wetting agents
what is the HLB mix equation?
[ f a HLB a ] + [f b HLB b ]
- will determine the final HLB value of a mix of surfactants
why do we need stabilisers?
, to attempt to keep 2 immiscible liquids mixed
- to reduce the interfacial tension between the separated phases
what are the steps of emsulion breakdown? EFCCB
Emuslion
Floculation
Coalescence
Creaming
Breaking
what is used to increase continuous phase viscosity?
methycellouse
what happens when you increase continuous phase
viscosity
the viscosity increases so there will be a decrease in flocculation
or coalescence rate as droplets will struggle to move/ disperse
a reduce creaming ratio
what is the creaming ratio equation?
CR= volume creamed/ total vol of emulsion
what is liquid paraffin?
the emulsion formed
an oil in water emulsion
what is the appropriate HLB value for liquid paraffin?
- higher HLB value
- as it is more hydrophilic
- the more hydrophilic the more suited for an o/w emulsion
- between 8-16
what is was used to investigate the effect of continuous
phase viscosity?
- 0.5% methycellulose
-2% methylcellouse
which emulsion was more stable of the aqueous phase?
2% methylcellulose solution
why was the 2% methylcellulose more stable?
1) higher viscosity- reduces creaming process
2) reduced coalescence- as it is more viscous and hard for oil
