WorksheetsITECH 25Oct2021
Total questions: 18
Worksheet time: 10mins
The most prevalent type of chain reactions is free radicalar polymerization
True
False
Free radicals are formed from
the homolytic cleavage of waek bonds
only the homolytic cleavage of covalent bonds
the homolytic cleavage of covalent bonds as well as numerous radiation-associated methods
only radiation-associated methods
A free radical is
a chemical specie that has two electrons (usually very reactive)
a chemical specie that has one free unpaired electron (usually very reactive)
a non reactive specie
an intermediate specie, atomic or molecular that has two electrons
In chain polymerization processes, the active center is retained at the middle of a growing polymer chain and monomers are added to this center in rapid succession.
True
False
The rate of addition of monomers to the active center relative to the overall conversion of the monomer to polymer is quite slow
True
False
In radicalar polymerization, high-molecular-weight polymers are generated even while most of the monomers remain intact
True
False
Polymers formed at the initial stage of the reaction are little affected by the extent of reaction and are of comparable molecular weight with those formed later in the reaction
True
False
The acquisition of the active site by the monomer is known as
the initiation step
the propagation step
the termination step
chain transfer effect
The destruction of the growth activity of the chain will lead to the
polymer and it is called step growth polymerization
polymer and it is called propagation step in chain growth polymerization
polymer and it is called initiation step in chain growth polymerization
polymer and it is called termination step in chain growth polymerization
In the study of Kinetics of Radicalar Polymerization, we assume that
there is just head-to-head propagation sub-steps, all with the same speed.
there is just head-to-tail propagation sub-steps, but all with different speed.
there is just head-to-tail propagation sub-steps, all with the same speed.
there is just tail-to-head propagation sub-steps, all with the same speed.
The initiation step in free-radical polymerization in the presence of thermal initiators is a two-step process, involving the homolysis of the relatively weak covalent bond in the initiator; and the generation of a new free radical
True
False
For diene monomers, the propagation mechanism is exactly the same as that of vinyl monomers, but the presence of two double bonds means either of two possible attacks can occur.
True
False
The termination steps can occur by either of two mechanisms: combination (coupling) or disproportionation
Combination is favoured by high temperatures
Disproportionation is favoured by low temperatures
Combination is favoured by low temperatures
they both can occur, independently on the temperature
When two growing polymer chains yield a single polymer molecule terminated at each end by an initiator fragment, we say that
initiation step is occuring
the polymer can grow
it occurs termination via combination
it occurs termination via disproportionation
.... involves hydrogen transfer with the formation of two polymer molecules, one with a saturated end and the other with an unsaturated terminal olefin and each with an initiator fragment
Initiation step
The growing of the polymer
Termination via combination
Termination via disproportionation
Steady state kinetics means that
all variables are constant in time (volume balance), just when there is not a flow through the system
all variables are constant in time (mass balance), even while there is a flow through the system
all variables are not constant in time (volume balance), even while there is a flow through the system
only some variables are constant in time (mass balance), even while there is a flow through the system
AUTOACCELERATION is also known as
Flory effect
Carothers effect
Trommsdorff effect
Schrodinger effect
Autoacceleration occurs
in highly exothermic reactions, where the transfer of heat is difficult
in highly endothermic reactions, where the transfer of heat is difficult
in highly exothermic reactions, where the transfer of heat is easy
in highly endothermic reactions, where the transfer of heat is easy
