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109 Cards in this Set
- Front
- Back
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_______ interactions must occur before chemical interactions or other processes can take place.
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Physical
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All _____ are miscible with one another, so two gases mixed are not considered to be an _______.
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Gases
Interface |
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Two examples of a surface / interface:
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Gas-Solid
Gas-Liquid |
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Force acting per unit length to minimize surface area of an interface:
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Surface Tension
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Two systems of measure:
CGS MKS |
cm grams seconds
meters kilograms seconds |
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Force applied to create displacement =
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Work
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Work can be used to measure _____ or _____ forces.
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cohesive or adhesive
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_______ forces are those that involve attraction of two different types of molecule.
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Adhesive
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_______ forces are those found between molecules of the same kind.
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Cohesive
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If cohesive forces are stronger than adhesive forces, a ________ will form at the interface.
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lens
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If adhesive forces are stronger than cohesive forces ________ will occur at the interface.
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Spreading
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Spreading may occur initially, until ________, where retraction occurs forming a lens.
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saturation
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Surface area per molecule is based on:
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# of molecules
spread surface are covered |
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A positive _______ means that spreading will occur
spontaneously |
S value > 0
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Spreading depends on the ______ _______ of the
liquids involved and on the _________ ______ between them |
surface tension
interfacial tension |
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Why do some solid particles need to be wetted prior to forming a suspension?
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The solid particles will be immersed in the liquid if the
liquid can replace the air that surrounds the particles |
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Often, to increase the extent of wetting, ________ _________
agents are used |
surface active
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The ________ ______ measures the tendency of the
liquid to wet the solid |
contact angle
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True or False
The smaller the contact angle, the lower the tendency of the liquid to wet the solid |
False
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θ = 0 = ________ wetting
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complete
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θ btw 0-180 = ________ wetting
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partial
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θ = 180 = ______ wetting
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no
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θ > ___ solid is not wettable by the liquid
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90
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θ btw Teflon and water is ____
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112 °
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_________ materials have small θ (lactose)
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hydrophilic
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hydrophobic materials have ___ θ
(magnesium stearate) |
large
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Contact Angle is governed by _______ equation
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Young's Equation
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Surfactants that assist in wetting by lowering the contact angle are called ________ _________.
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wetting agents
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The disadvantage of the Young’s equation is that it requires :
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knowledge of the interfacial tension Ysl and the surface tension of the solid Ys
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Alternative form of Young's equation with the advantage of not requiring interfacial tension or surface tension.
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S = Yl (cos θ – 1)
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Several methods are used to measure surface
tension or interfacial tension: |
1. Du Nouy ring method
2. Wilhemy plate method 3. Capillary rise |
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Du Nouy Ring method is used to measure both _____ _____ tension and interfacial _____ ____ tension
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liquid surface
liquid liquid |
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Du Nouy Ring employs a __________ that consists of a hanging platinumiridium
ring of defined geometry connected with a microbalance |
tensiometer
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Y = k F
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Du Nouy Ring equation
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Wilhemy Plate method requires hardware similar to the ring method however instead of a ring it uses _______ or a piece of ______ foil.
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mica glass
platinum |
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Wilhemy Plate equation:
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F = 2 (L + T) Y cos θ
L = length of plate T = thickness of plate |
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What is often true about the thickness of the plate in Wilhemy Plate equation / method?
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T is often negligible
T << L |
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Wilhemy method is mostly used when θ = ___ so the equation becomes.
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θ = 0
F = 2 x L x Y Y = F / 2 x L |
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The capillary rise method of determining surface tension is dependent on?
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The height to which the liquid rises inside the capillary tube.
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h = 2 Y cos θ / drg
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Capillary Rise equation for surface tension.
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The capillary rise equation can be simplified because
h = 2 Y / drg Y = drhg / 2 |
Capillary method is used mostly when θ = 0
cos θ = 1 |
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The surface of a solid can hold molecules of other substances
that come in contact with it. |
Adsorption
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Adsorption:
Molecules : Adsorbate Surface : |
Adsorbent
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Adsorption is typically studied at _____-_____ and _____-_____
interfaces |
gas-solid
liquid-solid |
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What roles does adsorption play in pharmacy
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Antidotes
Gas masks Purification Retardation of drug absorption Loss of drug in devices |
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If an adsorbate adsorbs onto an adsorbent by utilizing weak forces such as Van der Waals forces:
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Physical adsorption
Reversible |
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If an adsorbate adsorbs onto an adsorbent by utilizing strong
bonding such as covalent or ionic bonding: |
Chemisorption
Irreversible |
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both physical adsorption and chemisorption (w/ a few rare
exceptions) are ______ processes and _______ heat |
exothermic
liberate |
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Since adsorption is an exothermic phenomenon and releases heat,__________ will increase the amount adsorbed onto the solid.
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lowering the temperature
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An adsorption isotherm is a graph that shows the amount of adsorbate per adsorbent as a function of pressure for ______
or concentration for _____ at constant temp. |
gases
solutions |
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Three major types of adsorption isotherms are typically observed;
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– Langmuir
– Freundlich – BET |
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Describes the formation of a monolayer on the surface of the
solid adsorbent Indicative of chemisorption |
Langmuir isotherm
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______ isotherm can be used to measure the surface area of solids, since they represent adsorption of a _______ at the surface of the solid
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Langmuir
monolayer |
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The point of saturation when the _______ graph reaches a plateau is used to calculate:
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Langmuir
amount of gas adsorbed at the surface |
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x / M = abP / 1 + aP
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Langmuir Equation
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At very low pressures Langmuir reduces to:
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x / M = abP
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At very high pressures a limiting monolayer is reached :
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x / M = b
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Linear form of langmuir equation:
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P / (x / M) = (1 /ab) + (1 /b) P
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Freundlich isotherm represents ___________ adsorption: which depends on ______ forces of attraction
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multilayer physical
van der Waals |
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Freundlich does not reach ______ (plateau)
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saturation
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x / M = KP ^1/n
M = x = K = n = P = |
Freundlich isotherm
M = grams adsorbent x = amount adsorbed K + n = constants P = pressure of gas at equil. |
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Logarithmic form of Freundlich isotherm yields a straight line of logx/ M vs. log P
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logx / M = log K + 1/n x log P
Y = b + (M) (x) |
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logx / M = log K + (1 / n) (log P )
slope = intercept = |
slope = 1 / n
intercept = log K |
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Amiji: Stability problems
Adsorption of a protein to a polymer surface may catalyze protein ______ and ______ |
unfolding
aggregation |
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__% of human granulocyte colony-stimulating factor is adsorbed onto PVC container surfaces within the first 10min at 22C
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93%
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Containers that show the least amount of protein adsorption are: (3)
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untreated glass
silicone-treated glass propylene containers |
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____ , _____, _____ and _____ are among the factors that influence adsorption of proteins onto interfaces and solid surfaces.
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concentration
charge temperature hyrophobicity |
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Protein adsorption on surfaces is _______- dependent and for some proteins may reach saturation.
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concentration
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More insulin is adsorbed onto _______ surfaces than onto ______ surfaces
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hydrophobic
hydrophilic |
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Substances such as ______ at low concentrations of nonionic surfactants are added to reduce adsorptive losses of insulin and other proteins.
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albumin
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Pretreatment of surfaces with insulin will ______ adsorption of proteins.
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reduce
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When dispersed in the bulk of liquids, amphifilic substances will aggregate to the liquid interface reducing surface tension. =
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surfactants
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substances that are hydrophilic on one side and lipophilic on another =
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amphifiles
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Describes the electrophoretic mobility of particles in an
aqueous dispersion and has application in the design of pharmaceutical dispersions |
Zeta Potential
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potential that exists at the surface of the bound layer OR the potential difference between the surface of the bound layer and the region of electrical neutrality
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Zeta Potential
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Γ=-C/RT(dγ/dC)
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Gibbs Isotherm
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Gibbs isotherm describes behavior of soluble substances at ______-_____ interfaces and surfaces
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liquid-liquid
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Gibbs isotherm:
For sufactants Γ= ____ For surface inactive agents Γ= |
positive
negative |
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Surfactants can be classified as anionic, cationic, ______, and ______
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nonionic
zwitterionic |
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The surface active portion of an anionic surfactant has a ______ charge.
(sodium lauryl sulfate) |
negative
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_____ surfactants may have an unpleasant taste and skin irritation potential.
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Anionic
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Anionic surfactants are compatible with:
A. Cationic + nonionic surfactants B. Nonionic surfactants C. Zwitterionic + Nonionic Surfactants |
C
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Anionic Surfactant:
Sodium and potassium salts of straight-chain fatty acids = |
soaps
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Soaps are unstable below pH__ and yield water-insoluble free fatty acids
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pH7
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Soaps in the presence of ____, ____ , and aluminum yield water-insoluble precipitates
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calcium, magnesium
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Anionic Surfactant:
Sulfates such as sodium lauryl sulfate is used in ______, _____, and other cosmetics. |
toothpaste
shampoo |
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Anionic Surfactants:
The characteristic of this class is the sulfur atom connected to the carbon atom, less liable to hydolysis than sulfates. |
Sulfonates
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Anionic Surfactants:
N-Acyl taurines have good ____ compatibility with compatibility over a wide range of pH. |
skin
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Anionic Surfactants:
Monoalkyl phosphate demonstrates low _____ irritation and is used in _____ and _____ cleaners. |
skin
face body |
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Anionic Surfactants:
These are used in soaps and shampoos because of their mildness and foaming properties. |
Acyl isethionate
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N-Acyl sarcocinates produce a rich ______ and have excellent skin compatibility.
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foam
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______ surfactants can be used as bactericidal agents, conditioners and fabric softeners.
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Cationic
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Cations are compatible with ______ and _____ions
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nonions
zwitterions |
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Alkylbenzyldimethyl ammonium salts and Alkyltrimethyl ammonium salts are ______ surfactants used as ______
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Cationic
germicides |
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Unlike cationic and anionic surfactants, nonionic surfactants are not ______.
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electrolytes
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Polyoxyethylene alkyl ether = __________ surfactant
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nonionic
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Fatty acid alkanolamides = ________ surfactant
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nonionic
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Sorbitan fatty acid esters are ________ surfactants that form w/o emulsions
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nonionic
SPAN |
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SPAN is the commercial name for what nonionic surfactant?
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Sorbitan fatty acid esters
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TWEEN is the commercial name for what nonionic surfactant?
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Polyoxyethylene sorbitan fatty acid esters
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Alkyl polyglucoside nonionic is used for:
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dishwasher detergents and shampoos
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What is the main use of zwitterionic surfactants?
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Co-surfactants to boost foaming properties of other surfactants.
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The ________ film balance is an instrument can control the area of water surface available for the floating fatty acid molecules.
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Langmuir
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Lagmuir film balance plots _______ vs. ________
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surface pressure (pi symbol) vs.
area per molecule (A) |
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Benzoic acid as a preservative should partition into the _____ layer in the ________ form to be effective.
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lipid-like
un-dissociated |
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The benzoate ion is ineffective as a preservative because:
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it will not penetrate the cell membrane
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Benzoic acids efficacy as a preservative are dependent upon:
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pH
Partition coefficient Phase volume ratio |
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Benzoic acid in an emulsion exists in many forms:
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Oil
Benzoic acid dimers Benzoic acid Aqueous Benzoic acid Benzoate ion |
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C = Kq + 1 + Ka / (H)(Ha)w
name all variables |
C= original concentration in aqeuous phase
K= partition coefficient o/w q = Vo/Vw relative phase volume vo/vw Ha = concentration of undissociated acid in water phase |
