Polymer Molecular Mass Averages
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These flashcards cover key concepts related to Polymer Molecular Mass Averages to aid in exam preparation.
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22 Terms
Polymers are nearly always a mixture of macromolecules of different molar masses, represented as __.
Mi
The amount of macromolecules in a polymer is expressed by the number of molecules (Ni) or by the weight of the macromolecules (Wi = __).
NiMi
In a polymer sample, the molar mass of the repeating unit is __ g/mol.
100
The weight (Wi) of macromolecules is calculated using the formula __.
Wi = NiMi
The number of repeat units in the polymer can range from 1 to __.
5
For a polymer with 5 macromolecules, the total number of repeat units is __.
15
The number average molecular mass (Mn) is defined as __.
Mn = ΣNiMi / ΣNi
The weight average molecular mass (Mw) is calculated using __.
Mw = ΣWiMi / ΣWi
When all macromolecules are the same mass, Mn = Mw; however, for polymers, it is generally true that __.
Mn < Mw
The ratio of Mw/Mn is known as __ and characterizes the breadth of the molecular mass distribution.
dispersity (Ð)
Polymers are nearly always a mixture of macromolecules of different molar masses, represented as __.
Mi
The amount of macromolecules in a polymer is expressed by the number of molecules (Ni) or by the weight of the macromolecules (Wi = __).
NiMi
In a polymer sample, the molar mass of the repeating unit is __ g/mol.
100
The weight (Wi) of macromolecules is calculated using the formula __.
Wi = NiMi
The number of repeat units in the polymer can range from 1 to __.
5
For a polymer with 5 macromolecules, the total number of repeat units is __.
15
The number average molecular mass (Mn) is defined as __.
Mn = ΣNiMi / ΣNi
The weight average molecular mass (Mw) is calculated using __.
Mw = ΣWiMi / ΣWi
When all macromolecules are the same mass, Mn = Mw; however, for polymers, it is generally true that __.
Mn < Mw
The ratio of Mw/Mn is known as __ and characterizes the breadth of the molecular mass distribution.
dispersity (Ð)
What does a dispersity value equal to 1 (Ð = 1) indicate about a polymer sample?
It indicates that all macromolecules in the polymer sample have the exact same molar mass (monodisperse).
The statistical distribution of molecular masses in a polymer sample is primarily a result of __.
the inherent randomness and varying reaction rates during polymerization processes
Note 
Flashcards (27)