Quiz 4

Question 1

adsorbate

Answer 1

substance that is absorbed

Question 1

adsorbent

Answer 1

surface that absorbs it

Question 2

Interfacial tension

Answer 2

tension at the boundary between any two phases

Question 3

Surface tension

Answer 3

tension at the boundary between two phases where one of the phase
is gas

Question 4

why does surface tension decrease with temperature?

Answer 4

1. molecules moves faster and weakens the IMFs. Also leads to weaker cohesion and increased water vapor escape

Question 5

how does surface tension arise?

Answer 5

molecules at the surface experience a net inward force due to stronger cohesion with molecules below and adhesion of the water on top to the glass

Question 6

Adsorption

Answer 6

This is a surface phenomenon where molecules from a gas or liquid adhere to the surface of a solid or liquid

Question 7

Absorption

Answer 7

This is a bulk phenomenon where a substance is taken up into the volume of another material. In absorption, the absorbed molecules permeate through the entire bulk of the material. For example, a sponge absorbing water or gases being dissolved into a liquid.

Question 8

Surfactant

Answer 8

Surface active agents = amphiphiles: They reduce surface tension.

Question 9

Critical Micelle Concentration

Answer 9

Below the CMC, surfactant molecules are primarily located at the air-water interface, reducing surface tension.

At or above the CMC, the surface becomes saturated with surfactant molecules. Beyond this point, additional surfactant molecules can’t fit at the interface, so they start to aggregate together in the bulk solution, forming structures called micelles.

Question 10

how are micelles used in drug production?

Answer 10

reduce antigenicity by stealth action, solubilize a drug

Question 11

O/W emulsion (oil in water) and is a low or high HLB surfactant used?

Answer 11

small amount of oil in larger amount of water and shaken together to form a emulsion. A high HLB surfactant (hydrophilic) is used to reduce surface tension and makes the water surrounds the oil droplets, ensuring that water remains the continuous phase.

Question 12

W/O emulsion (water in oil) and is a low or high HLB surfactant used?

Answer 12

small amount of water in larger amount of oil and shaken together to form a emulsion. A low HLB surfactant (lipophilic) is used to make reduce the surface tension and makes the oil surround the water droplets, ensuring that oil remains the continuous phase.

Question 13

Can adsorption be physical or chemical?

Answer 13

adsorption can be both physical (Van der Waals forces) or chemical (irreversible because of the involvement of chemical bondings)

Question 14

Freundlich equation signifies

Answer 14

greater the Pressure, more would be the adsorption of that gas on an adsorbent

Question 15

Langmuir equation signifies

Answer 15

adsorption occurs as monolayer and it can be used for adsorption of both liquid as well
as a gas

Question 16

How does solubility affect adsorption?

Answer 16

Greater Solubility, Less Adsorption: Generally, the more soluble an adsorbate is in the solvent, the less it will be adsorbed onto a solid surface. This is because higher solubility means the adsorbate is more readily available in the solution rather than sticking to the adsorbent surface.
The order of solubility of iodine is CCl4>CHCl3>CS2
The order of adsorption of iodine is CS2>CHCl3>CCl4

Question 17

Are acidic or basic drugs more adsorbent

Answer 17

Acidic drugs are more adsorbent at low pH (acidic conditions) when they are non-ionized.
Basic drugs are more adsorbent at high pH (basic conditions) when they are non-ionized.

Question 18

A finer i.e. small size charcoal will adsorb more than a larger size one.

Answer 18

finer charcoal has a larger surface area due to the smaller particle size, which results in more adsorption sites.

Question 19

what is charcoal used for?

Answer 19

Charcoal is used in case of poisoning where it acts by gastrointestinal dialysis.

Question 20

Anionic surfactants (negatively charged)

Answer 20

substance that starts with sodium

Question 21

Cationic surfactants (positively charged)

Answer 21

substance that ends with bromide

Question 22

Amphoteric surfactants

Answer 22

lecithin

Question 23

Nonionic surfactants

Answer 23

Spans, Tweens, Pluronic F127

Question 24

Why does Bromopheniramine, chloroprocain, and chloropromazine work better than the original drugs?

Answer 24

Adding bromo or chloro group increases their surface activity, and decrease CMC so that the drug can form micelles earlier/easier

Question 25

Why is Cellulose acetate phthalate
used as enteric coating?

Answer 25

it forms a condensed film at pH 3 (in the stomach) but not at pH 6.5 and higher. So that the drug can be released in the intestine

Question 26

Exothermic processes are favored at reduced temperature; adsorption is an exothermic process,
think why?

Answer 26

increasing temperature increases solubility, so having lower solubility means better adsorption hence the adsorption is favored at a reduced temperature

Question 27

Why are surfactants with longer hydrophobic chain used for drugs that are more hydrophobic like phenobarbital?

Answer 27

Surfactants with a longer hydrophobic chain (e.g., Tween 80) tend to form larger micelles. This is beneficial for solubilizing drugs that are more hydrophobic, such as phenobarbital. Larger micelles can accommodate more of the hydrophobic drug within their core.

Question 28

Why use surfactants with bigger hydrophilic parts?

Answer 28

For drugs like dexamethasone, which are more polar, increasing the hydrophilic part of the surfactant (e.g., increasing the number of oxyethylene units) can enhance solubilization. In this case, even though the micelle size might be smaller, the increased number of micelles formed per mL provides more sites for solubilizing the drug

Question 29

Alkyl Chain Length

Answer 29

the longer the chain length, the more hydrophobic the compound and the less soluble it is

Question 30

Unsaturation

Answer 30

increase solubilization

Question 31

Cyclization

Answer 31

increase solubilization

Question 32

Steroidal Hormones:

Answer 32

For steroidal hormones, having a more polar group at the 17th carbon can increase solubility, as the polar groups interact better with the hydrophilic parts of micelles or solvents.

Question 33

what are Cresol, chlorocresol, and chloroxylenol solubilized in?

Answer 33

soap

Question 34

what surfactants are used in steroidal ophthalmic solutions?

Answer 34

Tween/Span

Question 35

what surfactants are used in Paclitaxel

Answer 35

Cremophor or trade name taxol

Question 36

When a capillary tube is immersed in benzyl benzoate, the liquid rose to a height of 1.63cm at 25C. The inside diameter of the capillary is 0.1 cm and the density of benzyl benzoate is 1.1120 g/cm3. What is the surface tension of benzyl benzoate?

Answer 36

y = (1/2) * rhpg
r = radius, *since given diameter, do 0.1/2
h = 1.63cm
p = 1.1120g/cm^3
g = 981cm/sec^2
y = (1/2) (0.05cm)(1.63cm)(1.1120g/cm^3)(981cm/sec^2) = 44.45 dynes/cm

Question 37

When 1 mL of a 0.009% (w/v) solution of stearic acid (Mol. Wt. 284.3 v) dissolved in a volatile organic solvent is placed on the surface of water in a trough, the solvent evaporates off, leaving the stearic acid spread over the surface as an insoluble monolayer film. If the surface area occupied by the film is 400 cm2, calculate the area occupied by each molecule of stearic acid in the film

Answer 37

0.009% w/v stearic acid = 0.009g/100mL
Therefore, 1 ml stearic acid * 0.009g/100mL = 0.00009g stearic acid
# of moles of stearic acid = 0.00009g / (284.3 g/mole) = 3.16 x 10-7 moles
Since 1 mole contains # of molecules equal to Avogadro number
Therefore, 3.16 x 10-7 moles * 6.022x10^23 molecules/mole = 1.91 x 10^17 molecules
Therefore, area occupied by one molecule = 400 cm2/1.91 x 10^17 molecules = 209.4x10^-17cm2/molecule

Question 38

The required HLB (RHLB) value for making an o/w emulsion is 10.9. Calculate the amounts of Tween 20 (HLB value 16.7) and Span 80 (HLB value 4.3) for making 2 g of the required emulsifiers.

Answer 38

𝑇ℎ𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑢𝑟𝑓𝑎𝑐𝑡𝑎𝑛𝑡 𝑤𝑖𝑡ℎ ℎ𝑖𝑔ℎ𝑒𝑟 𝐻𝐿𝐵 = 𝑅𝐻𝐿𝐵 ― 𝐻𝐿𝐵 𝑙𝑜𝑤
/ 𝐻𝐿𝐵 ℎ𝑖𝑔ℎ ― 𝐻𝐿𝐵 𝑙𝑜𝑤
Use the higher surfactant HLB first, so 𝑤𝑒𝑖𝑔ℎ𝑡 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑇𝑤𝑒𝑒𝑛 20 = 10.9 - 4.3 /
16.7 - 4.3 = 0.53
Therefore, the amount of Tween 20 = 2 g x 0.53 = 1.06 g
Then, the amount of Span 80 = 2 g – 1.06 g = .94 g

Question 39

Can water-insoluble vitamins such as vitamin A, D, E, and K be solubilized by surfactants?

Answer 39

yes