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1
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2
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3
Q

What is adsorption?

A

Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to an interface.

Adsorption differs from absorption, where a substance is absorbed into another material.

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4
Q

What are the two general types of adsorption?

A

Physical adsorption and chemical adsorption (chemisorption).

Physical adsorption involves weak van der Waals forces, while chemisorption involves stronger valence forces.

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5
Q

What characterizes physical adsorption?

A

Weak, reversible, multilayer adsorption.

The adsorbate is bound to the surface through weak van der Waals forces.

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6
Q

What is the nature of chemical adsorption (chemisorption)?

A

Involves stronger valence forces, seldom reversible, and typically forms a monolayer.

The adsorbate is not free to move in chemisorption.

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7
Q

What is an adsorption isotherm?

A

An equation that defines the relationship between the amount of adsorbate on the adsorbent and the pressure of the adsorbate at constant temperature.

Common isotherms include Freundlich, Langmuir, and BET.

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8
Q

What does the Freundlich isotherm describe?

A

It describes the amount of gas absorbed plotted against the equilibrium pressure of the gas at constant temperature.

It is an empirical relationship, often used for heterogeneous surfaces.

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9
Q

What is the Langmuir isotherm?

A

It describes adsorption on a surface with a finite number of identical sites, leading to a monolayer coverage.

It assumes no interaction between adsorbate molecules.

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10
Q

What does BET stand for in adsorption isotherms?

A

Brunauer, Emmett, and Teller.

The BET theory is used to describe multilayer adsorption.

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11
Q

What happens to adsorption as pressure increases?

A

Adsorption tends to reach a limiting value as pressure increases.

Initially, adsorption increases rapidly with pressure.

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12
Q

What is the equation for adsorption in terms of mass of gas adsorbed?

A

log(x/m) = log(k) + n log(P)

Where x is the mass of gas adsorbed, m is the mass of the adsorbent, P is the equilibrium gas pressure, k and n are constants.

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13
Q

True or False: In physical adsorption, the adsorbate is free to move.

A

True.

This is a key characteristic distinguishing it from chemisorption.

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14
Q

Fill in the blank: The contact angle method is used to measure _______.

A

wetting properties.

The contact angle indicates how a liquid interacts with a solid surface.

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16
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17
Q

What is the HLB value of a surfactant when the saponification number is 45.5?

A

276

The HLB (Hydrophilic-Lipophilic Balance) value indicates the balance between the hydrophilic and lipophilic portions of a surfactant.

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18
Q

What is the HLB value of Polyoxyethylene sorbitol beeswax derivative (G1706)?

A

20

HLB values help determine the appropriate surfactant for a specific application.

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19
Q

What is the HLB value of Sorbitan tristearate?

A

20

This surfactant is commonly used in emulsification processes.

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20
Q

What is the HLB value of Glyceryl monostearate?

A

16.7

Glyceryl monostearate is often used as an emulsifier in food and cosmetics.

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21
Q

What is the HLB value of Sorbitan monooleate (Span 80)?

A

4.3

Span 80 is a non-ionic surfactant used for food and pharmaceutical applications.

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22
Q

What is the HLB value of Diethylene glycol monostearate?

A

9.5

This compound is often used in personal care formulations.

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23
Q

What is the HLB value of Sorbitan monolaurate (Span 20)?

A

4.7

Span 20 is used in emulsifying and stabilizing food products.

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24
Q

What is the HLB value of Polyethylene lauryl ether (Brij 30)?

A

12

Brij 30 is used in various cosmetic formulations as a surfactant.

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25
What is the HLB value of Polyoxyethylene monostearate (Myrj 45)?
16.9 ## Footnote Myrj 45 is used in pharmaceuticals for its emulsifying properties.
26
What is the HLB value of Sodium oleate?
18 ## Footnote Sodium oleate is used in soap making and as an emulsifier.
27
What is the HLB value of Polyoxyethylene sorbitan monooleate (Tween 80)?
15 ## Footnote Tween 80 is widely used in food and pharmaceutical industries for emulsification.
28
What is the HLB value of Polyoxyethylene sorbitan monolaurate (Tween 20)?
16.7 ## Footnote Tween 20 is commonly used in food and cosmetics as an emulsifier.
29
What is the HLB value of Polyoxyethylene lauryl ether (Brij 35)?
13.2 ## Footnote Brij 35 is utilized in various applications, including personal care products.
30
What is the HLB value of Potassium oleate?
20 ## Footnote Potassium oleate is used in soap formulations and as an emulsifier.
31
What is the HLB value range for Sodium lauryl sulfate?
7-9 ## Footnote Sodium lauryl sulfate is often used as a surfactant in cleaning products.
32
What does a contact angle of 0° indicate?
Complete wetting ## Footnote A contact angle of 0° means that the liquid fully spreads on the surface.
33
What does a contact angle greater than 90° indicate?
Non-wetting ## Footnote A contact angle greater than 90° means that the liquid does not spread on the surface.
34
What is the definition of wetting?
The extent of contact between a liquid and surface ## Footnote Wetting is crucial in applications involving liquids interacting with solid surfaces.
35
What is a wetting agent?
A surfactant that lowers the advancing contact angle ## Footnote Wetting agents help to displace air at the surface and replace it with a liquid phase.
36
Fill in the blank: The degree of wetting is defined as the extent to which a liquid _______ on a surface.
contacts ## Footnote The degree of wetting is essential in understanding how liquids behave on surfaces.
37
True or False: A contact angle of 180° indicates perfect wetting.
False ## Footnote A contact angle of 180° indicates a perfectly non-wetting surface.
38
What is the HLB value of Triethanolamine oleate?
16.7 ## Footnote Triethanolamine oleate is used in various formulations for emulsification.
39
40
What are the main classes of surfactants?
* Cationic * Anionic * Non-ionic * Ampholytic
41
What are examples of cationic surfactants?
* Quaternary ammonium salts * Pyridinium compounds
42
What are examples of anionic surfactants?
* Alkali soap * Sodium lauryl sulfate
43
What does HLB stand for?
Hydrophilic Lipophilic Balance
44
Who developed the HLB system and when?
Griffin in 1949
45
What is the HLB value for Polyoxy ethylene mono oleate?
80
46
What HLB value indicates a lipophilic surfactant?
> 20
47
What is the HLB value range for wetting and spreading agents?
(7 - 9)
48
What is the HLB value range for detergents?
(13 - 15)
49
What is the formula to determine HLB values?
HLB = (Hydrophilic group no.) - (Lipophilic group no.) + 7
50
What type of surfactant is Cetyl trimethyl ammonium bromide?
Cationic surfactant
51
What is the HLB value for solubilizing agents?
(16 - 18)
52
Fill in the blank: The HLB system is used to classify _______.
Surfactants
53
What is the HLB value for Polyoxy ethylene mono laurate?
> 20
54
What is the HLB value for Polyoxy ethylene mono palmitate?
40
55
What is the HLB value for Polyoxy ethylene mono stearate?
> 60
56
What is the characteristic of a surfactant with an HLB value below 10?
Lipophilic
57
What is the characteristic of a surfactant with an HLB value above 10?
Hydrophilic
58
What is the HLB range for O/W emulsifying agents?
(8 - 16)
59
What is the HLB range for W/O emulsifying agents?
(3 - 8)
60
What is an example of a hydrophilic surfactant?
Sodium lauryl sulfate
61
What is an example of a lipophilic surfactant?
Cetyl trimethyl ammonium bromide
62
True or False: The HLB system is an arbitrary scale for expressing the hydrophilic and lipophilic characteristics of an emulsifying agent.
True
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PHYSICAL PHARMACY (1 decks)

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