This set of Multiple Choice Questions & Answers (MCQs) focuses on “Nanomaterials – Set 7”.
1. If a porous molecule has pore size smaller than 2 nm, it is called________
a) Microporous
b) Mesoporous
c) Macro-porous
d) Xerogel
View Answer
Explanation: Microporous materials have pore size smaller than 2 nm while mesoporous materials have pore size between 2 nm to 50 nm and macro-porous material has pore size bigger than 50 nm. Xerogels are a type of mesoporous material.
2. Cetyl tri-methyl ammonium bromide, CTAB, is a ______
a) Cationic surfactant
b) Anionic surfactant
c) Amphoteric surfactant
d) Non-ionic surfactant
View Answer
Explanation: CTAB has an ammonium group, which have positive charge so it is an anionic surfactant. Anionic surfactant has negative charge on hydrophilic part and amphoteric has both charges on hydrophilic part. Non-ionic surfactant has no net charge on its hydrophilic part but it has some polarity.
3. Which micelles is used for the formation of mesoporous materials?
a) Simple micelles
b) Cubic micelles
c) Cylindrical micelles
d) Laminar micelles
View Answer
Explanation: When the concentration of surfactant molecule reaches above the critical micelle concentration, micelles are formed. If concentration of surfactant molecules are increased further, cylindrical micelles are formed which aggregates into cubic micelles on further increase of concentration. This structure forms ordered mesoporous materials.
4. Aerogel & xerogel is an example of _______
a) Ordered mesoporous material
b) Random mesoporous material
c) Zeolites
d) Core shell structure
View Answer
Explanation: Mesoporous materials formed by micelle formation is ordered mesoporous materials. Zeolites and core shell structure are the structures with crystalline pore allocation. Aerogels and Xerogel are the structures in which pores are allocated randomly as they are formed by evaporation of solvent.
5. Which mesoporous material is made by sol-gel synthesis under ambient conditions?
a) Aerogels
b) Xerogels
c) Zeolites
d) Ordered mesoporous materials
View Answer
Explanation: Zeolites are crystalline structures and they are synthesized by various different methods not by sol-gel method. Ordered mesoporous materials are synthesized by micelles, Aerogels are made by sol-gel synthesis but under supercritical conditions. Xero-gels are made by sol-gel synthesis under ambient conditions.
6. Zeolites are ____
a) Ordered mesoporous material
b) Random mesoporous material
c) Crystalline mesoporous material
d) Core shell structure
View Answer
Explanation: Zeolites have a crystalline structure, so they have pores with special locations. Pores are not randomly oriented like random mesoporous material in zeolites, as zeolites have pore size of order of 2 to 50 nm hence zeolites are crystalline mesoporous materials.
7. When the concentration of surfactant molecule is higher than critical micelle concentration, which structure is formed first?
a) Spherical micelle
b) Cylindrical micelle
c) Cubic micelle
d) Laminar micelle
View Answer
Explanation: When concentration of surfactant molecules increases the critical concentration, then surfactant molecules aggregate themselves to form spherical micelles, these micelles then form cylindrical micelles, which again forms cubic micelle and then laminar micelle with increase of concentration.
8. At which point, difference between gaseous and liquid disappears?
a) Boiling point
b) Freezing point
c) Triple point
d) Critical point
View Answer
Explanation: At freezing point, solid and liquid phases co-exist but are separable from each other. Same way at boiling point and triple point, liquid-gas and solid-liquid-gas phases coexist but are separable but above critical point liquid and solid phases disappear.
Sanfoundry Global Education & Learning Series – Nanomaterials.
To practice all areas of Nanomaterials, here is complete set of Multiple Choice Questions and Answers.
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