Pulp and Paper Multiple Choice Questions on “Molecular Weight of Polymers”.
1. __________ consist of individual polymers with varying molecular weights. The properties of the polymers depend on the distribution of molecular weights.
a) Monodisperse
b) Polydispersity
c) Cellulose chain
d) Synthetic polymer
Answer: a
Clarification: Synthetic polymers consist of individual polymers with different molecular weights. The properties of the polymers depend not only on the average molecular weight but on the distribution of molecular weights as well.
2. Several methods utilized to characterize polymers give average molecular weights that depend on the molecular weight distribution as well as the number average molecular weight.
a) True
b) False
Answer: a
Clarification: Most of the methods are utilized to characterize polymers give average molecular weights that depend on the molecular weight distribution as well as the number average molecular weight.
3. A __________ depicted as Mn, Let Ni equal the number of the molecules or moles or other calculated of number of molecules with mass M, or a calculated of mass such as D.P.
a) Number average molecular weight
b) Number mean molecular weight
c) Number median molecular weight
d) Number mode molecular weight
Answer: a
Clarification: The 1st is a simple average where each molecule contributes equally to the average a number average molecular weight depicted as Mn. Let Ni equal the number of the molecular or moles or other measure of number of molecular with mass M, or a measure of mass such as D.P.
4. A number average molecular weight is obtained by methods that solely depend on the colligative properties of polymer solutions.
a) True
b) False
Answer: a
Clarification: A number average molecular weight is extracted by methods which solely depend on the colligative properties of polymer solutions.
5. One such method is vapour phase __________ that indirectly measures vapor pressures of polymer solutions.
a) Symmetry
b) Osometry
c) Isentropic
d) Adiabatic
Answer: b
Clarification: Such methods are limited to low molecular weight polymers several thousand grams per mole or less. This method has the drawback that it does not represent the behaviour of polymer mixtures very well. Vapor phase osmometry indirectly measures vapour pressures of polymer solutions.
6. The __________ is always higher than the number average molecular weight, except for the special case when they are equal if all of the polymers have the exact same molecular weight.
a) Weight average molecular weight
b) Weight average cation weight
c) Weight average anion weight
d) Weight average quinon weight
Answer: a
Clarification: The weight average molecular weight is always greater than the number average molecular weight, except for the special case when they are equal if all of the polymers have the exact same molecular weight example a monodisperse sample, the ratio is then greater than one.
7. What is the name of the hidden part?
a) Number average molecular weight
b) Weight average
c) Monodisperse
d) Polydispersity
Answer: a
Clarification: The number average molecular weight is the total weight of the sample divided by the number of molecules in the sample. It could be calculated by the above formula for the react.
8. What is the name of the hidden part?
_________= (ΣNi x ΣMi) / (ΣNi)
a) Number average molecular weight
b) Weight average
c) Monodisperse
d) Polydispersity
Answer: a
Clarification: Then number average molecular weight is the total weight of the sample divided by the number of molecules in the sample. It could be calculated by the above formula for a particular react.
9. What is the name of the hidden part?
________= (ΣNi x ΣDPi) / (ΣNi)
a) Number average molecular weight
b) Weight average
c) Monodisperse
d) Polydispersity
Answer: b
Clarification: A weight average molecular weight is determined by light scattering methods but is limited to relatively great molecular weights.
10. What is the name of the hidden part?
_________ = (ΣNi x ΣDP2i) / (ΣNi x DPi)
a) Number average molecular weight
b) Weight average
c) Monodisperse
d) Polydispersity
Answer: b
Clarification: A weight average molecular weight is calculated by light scattering methods but is limited to relatively great molecular weights.
>