Unit Processes Mcqs

Q:

Osmotic pressure cannot be used to determine the molecular weight.

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: Another related method of determining molecular weights is based on the osmotic pressure of a solvent-solute system.

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24
Q:

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
 
Answer & Explanation Answer: D) All of the mentioned

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.

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21
Q:

The kinetics of ionic polymerization has common principles with which polymerization?

A) Addition B) Pearl
C) Free-radical D) Ion exchange
 
Answer & Explanation Answer: C) Free-radical

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.

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22
Q:

How is the degree of polymerization of the polymer obtained?

A) Termination/ Propagation B) Propagation/ Termination
C) Propagation* Termination D) None of the mentioned
 
Answer & Explanation Answer: B) Propagation/ Termination

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.

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16
Q:

An important parameter in all polycondensations is the “extent of reaction”.

A) True B) False
 
Answer & Explanation Answer: A) True

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.

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27
Q:

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
 
Answer & Explanation Answer: C) All of the mentioned

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.

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24
Q:

What is the other name of ‘Pearl’ polymerisation?

A) Emulsion B) Heterogeneous
C) Suspension D) None of the mentioned
 
Answer & Explanation Answer: C) Suspension

Explanation: Pearl (Suspension) Polymerization. The method of emulsion polymerization has proved highly efficient for large-scale production of polymers of high average molecular weight.

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24
Q:

During emulsion polymerisation particle size decreases.

A) True B) False
 
Answer & Explanation Answer: A) True

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.

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