This set of Unit Processes Multiple Choice Questions & Answers (MCQs) focuses on “Methods of polymerization”.
1. Bulk polymerization requires which type of monomer?
a) Gaseous
b) Liquid
c) Both gaseous and liquid
d) None of the mentioned
View Answer
Explanation: Bulk (Mass) Polymerization. This type of polymerization is accomplished by subjecting the liquid or gaseous monomer to polymerizing conditions.
2. What is the disadvantage of bulk polymerization?
a) High temperature
b) Heat control
c) Need catalyst
d) All of the mentioned
View Answer
Explanation: The disadvantage of a continuous and elaborate heat control, which is necessary in bulk polymerization, is completely overcome if the monomers are dissolved in suitable solvents and the polymerizations carried out in solution.
3. What are the factors of solution polymerisation?
a) Nature of solvent
b) Concentration
c) Temperature
d) All of the mentioned
View Answer
Explanation: Thus the nature of the solvent and the concentration of the monomer are the determining factors for the progress of the polymerization at a certain temperature, which progress, however, never reaches the speed of a bulk polymerization.
4. During emulsion polymerisation particle size decreases.
a) True
b) False
View Answer
Explanation: During emulsion polymerization under the influence of heat and appropriate catalysts, the average particle size decreases to about one-tenth of its starting size, and the polymer is usually obtained in the form of a very stable emulsion called a latex.
5. What is the other name of ‘Pearl’ polymerisation?
a) Emulsion
b) Heterogeneous
c) Suspension
d) None of the mentioned
View Answer
Explanation: Pearl (Suspension) Polymerization. The method of emulsion polymerization has proved highly efficient for large-scale production of polymers of high average molecular weight.
6. What is the principal feature of a polycondensation?
a) Stable intermediate
b) Rate of condensation is independent
c) All of the mentioned
d) None of the mentioned
View Answer
Explanation: The principal feature of a polycondensation are: (1) that all the intermediate species are stable molecules and (2) that the rate of condensation is independent of the degree of polymerization, Le., the reactivity of the functional groups is independent of the molecular weight of the molecule to which it is attached.
7. An important parameter in all polycondensations is the “extent of reaction”.
a) True
b) False
View Answer
Explanation: An important parameter in all polycondensations is the “extent of reaction,” i.e., the fraction of the reactive groups which have reacted up to a specified time t.
8. How is the degree of polymerization of the polymer obtained?
a) Termination/ Propagation
b) Propagation/ Termination
c) Propagation* Termination
d) None of the mentioned
View Answer
Explanation: The degree of polymerization of the polymer is obtained from the ratio of the propagation reaction to that of termination, or the ratio of the propagation reaction to that of initiation, since in the steady state the initiation and termination rates are equal.
9. The kinetics of ionic polymerization has common principles with which polymerization?
a) Addition
b) Pearl
c) Free-radical
d) Ion exchange
View Answer
Explanation: The kinetics of ionic polymerization share some common principles with that of the free-radical reaction. Both are based on the basic steps of initiation, propagation, termination, and chain transfer, and in both the ultimate average molecular weight depends on the ratio of the reaction rates of propagation and termination.
10. Which phenomena arise because of the requirements of thermodynamic equilibrium between two phases?
a) Freezing-point depression
b) Vapour-pressure drop
c) Boiling-point elevation
d) All of the mentioned
View Answer
Explanation: The freezing-point depression, vapour-pressure drop, and boiling-point elevation of a liquid caused by the presence of a dissolved solute are a set of closely related phenomena which arise because of the requirements of thermodynamic equilibrium between two phases.
11. Osmotic pressure cannot be used to determine the molecular weight.
a) True
b) False
View Answer
Explanation: Another related method of determining molecular weights is based on the osmotic pressure of a solvent-solute system.
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