15 Questions
What is the primary reason for the presence of interfacial tension at the interface between two immiscible liquids?
Differences in molecular polarity
What is the result of a positive spreading coefficient when a liquid is placed on a solid surface?
The liquid will spread and have a low contact angle
What is the primary mechanism by which surfactants reduce interfacial tension between two liquids?
Insertion of the hydrophobic tail into one liquid and the hydrophilic head into the other
What is the primary application of surfactants in cosmetic formulations?
To improve the skin penetration of active ingredients
What is the primary concern when formulating a topical product for skin application?
The product's surface tension and wetting properties
What is the primary purpose of displacing air from the surface of sulfur, charcoal, and other powders in pharmaceutical applications?
To facilitate the dispersal of these drugs in liquid vehicles
Which of the following is an example of the application of wetting in medicine?
The use of detergents in the washing of wounds
What is the primary role of the spreading coefficient in determining the effectiveness of topical creams and lotions?
It influences the uniform distribution of the active ingredients on the skin surface
What is the primary benefit of using surfactants in cosmetic formulations?
They facilitate the spreading and wetting of the skin surface
Which of the following is an example of interfacial tension in pharmaceutical applications?
The interaction between a lotion and the skin surface
What is the primary location of non-polar molecules in aqueous systems when the concentration of surface active agents exceeds the CMC?
In the hydrocarbon core of the micelle
What is the primary function of the hydrophile-lipophile balance (HLB) number?
To determine the balance between hydrophobic and hydrophilic portions of a surfactant
What is the effect of increasing the concentration of a surface active agent on the solubility of a slightly soluble substance?
The solubility increases sharply
Why do surfactants protect their hydrophobic groups from the aqueous environment?
To prevent their exposure to the aqueous environment
What is the result of the ability of a surfactant to solubilize a drug in an aqueous environment?
Increased solubility of the drug
Study Notes
Interfacial Phenomena
- The boundary between two phases is known as an interface.
- Examples of wetting in pharmacy and medicine:
- Displacing air from powder surfaces to disperse drugs in liquid vehicles.
- Displacing dirt with detergents in wound washing and applying medicinal lotions/sprays to skin and mucous membranes.
Spreading Coefficient
- Lotions, creams, sunscreens, and cosmetics require spreading on the skin to be effective.
- Spreading allows hydrophobic groups to be protected from the aqueous environment.
Effect of Surfactant on Solubility
- The ability of a solution to solubilize a drug increases sharply when the surfactant concentration exceeds the Critical Micelle Concentration (CMC).
- Nonpolar molecules in aqueous systems are located in the hydrocarbon core of the micelle, increasing solubility.
Hydrophile-Lipophile Balance (HLB)
- HLB is a measure of the balance between hydrophobic and hydrophilic portions of a surfactant.
- HLB number is a key factor in determining the properties of a surfactant.
This quiz covers the concept of interfacial phenomena, including wetting and spreading coefficient, and their applications in pharmacy and medicine.
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