This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Nanoparticles – Colloids”.
1. What is the main difference between colloids and crystalloids?
a) Solubility
b) Reactivity
c) Particle size
d) Electrical nature
View Answer
Explanation: Colloid is a mixture in which very small particles of a substance remain dispersed throughout another substance or medium. Crystalloids, on the other hand, are the aqueous solution of mineral salts or water soluble molecules. These two substances mainly differ in particle size. Colloids contain larger particles than crystalloids.
2. What happens when the ferric chloride solution is added to freshly precipitated ferric hydroxide?
a) Green coloured colloid
b) Brown coloured colloid
c) Red coloured colloid
d) Blue coloured colloid
View Answer
Explanation: When ferric chloride solution is added to freshly precipitated ferric hydroxide, a brown coloured colloidal solution is obtained. This happens due to the adsorption of ferric ions on the surface of precipitate. The accumulation of ferric ions on the surface causes repulsion between them and results in the fragmentation of large precipitate particles into small colloidal particles.
3. What happens when a soap bubble is charged?
a) Soap bubbles attract each other
b) Soap bubbles decrease in size
c) Soap bubbles increase in size
d) Soap bubbles remain unaffected
View Answer
Explanation: When a soap bubble is charged, it expands and grows in size because the charged particles are uniformly distributed on it. These cause electrostatic repulsive forces to act between similar charges.
4. The given reaction produces colloid. What kind of a technique is followed according to this reaction?
As2O3 + 3H2S ➔ As2S3 + 3H2O
a) Oxidation techniques
b) Hydrolysis technique
c) Double decomposition technique
d) Esterification technique
View Answer
Explanation: Hydrophilic or Lyophobic colloidal sols can be prepared by various techniques. Double decomposition method is one such technique in which sols of inorganic insoluble salts such as arsenous sulphide, silver halides etc are prepared. Example:- When hydrogen sulphide is made to pass through a dilute aqueous solution of arsenous oxide a colloidal solution of arsenous chloride is obtained.
5. Which method of colloid purification uses a phenomenon of diffusion through a permeable membrane?
a) Electrodialysis
b) Electrodecantation
c) Dialysis
d) Ultrasonic dispersion
View Answer
Explanation: Dialysis is a method of purification of colloidal solutions from which ions are removed by diffusion through a permeable membrane. Example: – Ferric hydroxide sol can be purified using this method.
6. Bredig arc’s method is not used for the preparation of sols of which of the following metal sols.
a) Gold
b) Platinum
c) Silver
d) Vanadium
View Answer
Explanation: Bredig arc’s method, also known as electro – dispersion method is used for the preparation of metal sols of gold, silver and platinum. This method is not suitable when the condensation phase or the dispersion medium is an organic liquid since it causes considerable charring.
7. What is the correct order of process followed in the mechanical dispersion method for colloid formation?
a) Particles are grinded ➔ Suspension of the substance is added into mill ➔ Addition of inert diluents ➔ Dispersion in water forming sols
b) Addition of inert diluents ➔ Particles are grinded ➔ Dispersion in water forming sols ➔ Suspension of the substance is added into mill
c) Suspension of the substance is added into mill ➔ Particles are grinded ➔ Dispersion in water forming sols ➔ Addition of inert diluents
d) Dispersion in water forming sols ➔ Suspension of the substance is added into mill ➔ Addition of inert diluents ➔ Particles are grinded
View Answer
Explanation: Mechanical dispersion method uses a colloid mill to form the colloidal sols. In this process a suspension of the substance in water is added to the mill. This grinds the particles of the suspension into colloidal size and gets dispersed in water to form a sol. Sometimes, to obtain a finer dispersion, inert diluents are added to the sols inorder to prevent the growth of colloidal particles in size.
8. What is the size range of colloidal particles?
a) < 10-7 cm
b) 10-17 to 10-12 cm
c) > 10-5 cm
d) 10-7 to 10-5 cm
View Answer
Explanation: A colloidal solution has particles in it in the range of 1nm to 1μm in size which is larger than most ordinary molecules but still way too small to be seen by the naked eyes. In centimeters the particle size ranges between 10-7 to 10-5 cm.
9. Identify a factor that is not responsible for bringing stability to colloidal particles.
a) Treatment with polymeric molecules
b) Steric hindrance
c) Flocculation
d) Repulsion of colloidal particles
View Answer
Explanation: Colloids can be stabilized by the addition of polymers to the dispersion medium that inhibit the flocculation of colloidal particles. These solutions can be stabilized by Coulombic repulsions that arise due to the presence of similar charges on their surface. Sometimes surface passivating molecules can be used to provide stearic hindrance preventing coalescence or aggregation.
10. Define Collodion.
a) Colloidal emulsion of nitrocellulose in water
b) Colloidal sols of cellulose nitrate in ether and alcohol
c) Colloidal gel of cellulose acetate in ethyl alcohol
d) Colloidal foam of cellulose anhydride in ether
View Answer
Explanation: Collodion is a colloid of the type sol which is made up of cellulose nitrate ether and alcohol. It has a boiling point of about 34°C. It is usually applied as an adhesive to close small wounds and hold surgical dressings. It can be used to make photographic plates.
11. Blue eye colour of a person is due to Tyndall scattering.
a) True
b) False
View Answer
Explanation: The blue iris in an eye is due to Tyndall scattering in the translucent layer in the iris. Scattering takes place mostly in the shorter wavelength region while the longer wavelengths tend to pass through the translucent layer unaltered. Since, the shorter wavelengths are blue wavelength this results in a blue hue in the light coming out of the eye.
12. Who observed electrophoresis for the first time?
a) Iijima and Robert F. Curl
b) Krätschmer and Huffmen
c) Sir Harold W.Kroto and Richard E.Smalley
d) Peter Ivanovich Strakhov & Ferdinand Frederic Ruess
View Answer
Explanation: The electrokinetic phenomenon of electrophoresis was discovered by Russian professors Ferdinand Frederic Ruess and Peter Ivanovich Strakhov in 1807 at Moscow University. They were able to observe the migration of clay particles dispersed in water upon application of a constant electric field.
13. Which form of colloid has gaseous particles dispersed in solid or liquid?
a) Sol
b) Foam
c) Gel
d) Emulsion
View Answer
Explanation: Foam is a type of colloid formed when gaseous particles remain dispersed in a liquid or solid medium. Example:- Whipping cream. Solid foams exist that have either closed cell or open cell. In closed cell foam gas forms discrete pockets, while in open cell foam gas pockets remain connected to each other.
14. Who discovered Tyndall effect?
a) Pearl Esther Tyndall
b) William Tyndall
c) John Tyndall
d) Louisa charlotte Tyndall
View Answer
Explanation: Tyndall effect was discovered as well as named after the Irish physicist John Tyndall. It is also referred to as Willis-Tyndall scattering. The first steps towards explaining the reason behind the colour of the sky were taken by him in 1859.
15. What expression is used to depict the distance travelled by a colloidal particle between successive collisions?
a) \(\overline {\Delta R^2} \) = (k/3ηπr) Δt
b) \(\overline {\Delta R^2} \) = (k2T2/3ηπ) Δt
c) \(\overline {\Delta R^2} \) = (kT/3ηπr) Δt
d) ΔR = (kT/3ηπ) Δt
View Answer
Explanation: Colloidal particles undergo Brownian motion. The particles make random movements, hitting each other and changing direction of motion in solution. The distance travelled between successive collisions on an average is given as;
\(\overline {\Delta R^2} \) = (kT/3ηπr) Δt
Here, k=Boltzmann’s constant, T=Temperature of the liquid, r = Radius of particle, Δt = Time and η = viscosity of liquid.
Sanfoundry Global Education & Learning Series – Nanotechnology.
To practice all areas of Nanotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]
