This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Foams”.
1. _________ are large air bubbles separated by thin films of liquid with thicknesses in the range of those of colloids.
a) Foams
b) Froth
c) Monolayer
d) Synergistic effect
View Answer
Explanation: Foam, in physical chemistry, a colloidal system i.e., a dispersion of particles in a cont. medium into which the particles are gas bubbles and the medium is a liquid. They decrement the rate of water drainage at the junction of 3 gas bubbles, the plateau borders.
2. Foams are relatively unstable with lifetimes that increment with increasing viscosity of the liquid phase.
a) True
b) False
View Answer
Explanation: Foams are large air bubbles differentiated by thin films of liquid with thicknesses in the range of those of colloids. The term also is applicable to material in a lightweight cellular spongy or rigid form.
3. _________ are important because they are utilized in froth flotation deinking and because they are detrimental in many other aspects of pulping and papermaking.
a) Foams
b) Froth
c) Monolayer
d) Brown stock washing
View Answer
Explanation: In most foams, the volume of gas is big, with thin films of liquid or solid separating the regions of gas. They come under the category of dispersed media.
4. Froth flotation of minerals uses a surfactant to attach to the mineral particles, making them _________ and a foaming agent to stabilize the foam that is formed.
a) Hydrophilic
b) Hydrophobic
c) Deinking
d) Evaporate
View Answer
Explanation: It is the process of removing printing ink from paper fibres of recycled paper. This is accomplished by a combination of mechanical action and chemical means.
5. Agents used to induce foam are selected empirically, although a few rules can act as guidance.
a) Surfactants
b) Foams
c) Agents
d) CMC
View Answer
Explanation: Froth flotation of minerals utilises a surfactant to attach to the mineral particles, making them hydrophobic, and a foaming agent to stabilize the foam that is formed.
6. Surfactants used near their C.M.C. are particularly effective since they can form monolayers.
a) Surfactants
b) Foams
c) Agents
d) CMC
View Answer
Explanation: Usually mixtures of surfactants have a synergistic effect toward inducing foam formation. It is defined as the concentration of surfactants above which micelles form and all additional surfactants added to the system go to micelles.
7. Which of the following is utilized in foam formation?
a) Minerals
b) Vitamins
c) Proteins
d) Starch
View Answer
Explanation: Proteins are sometimes useful in foam formation, as anyone who has beaten an egg white or cream knows. These foams are formed by denaturing of the proteins.
8. _________ can sometimes be destroyed by blowing hot air on them.
a) Surfactants
b) Foams
c) Agents
d) CMC
View Answer
Explanation: This lowers the viscosity of the liquid and helps evaporate liquid at the interfaces. Gas is % in large amount so it’ll be divided into gas bubbles of many different sizes separated by liquid regions which may form films, thinner and thinner when the liquid phase is drained out of the system films.
9. Some surface active chemicals that do not stabilize the foam can displace the surfactants that do stabilize the _________
a) Surfactants
b) Foams
c) Agents
d) CMC
View Answer
Explanation: A crucial division of solid foams is into closed-cell foams and open-cell foams. In a closed-cell foam, the gas forms discrete pockets which are completely surrounded by the solid material.
10. Low molecular weight alcohols or fatty acids (4-6 carbon atoms) can also act as _________
a) Fat
b) Vitamin
c) Protein
d) Deformers
View Answer
Explanation: Ca2+ may decrement the foaming tendency of fatty acid soaps by rendering them insoluble, like taking a bath in hard water. It is a chemical additive that reduces and obstructs the formation of foam in industrial process liquids.
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