Molecular Mass Calculation in Chemistry Blend

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Questions and Answers

What process did Charles Goodyear discover to greatly improve the properties of the polymer?

  • Sulfurization (correct)
  • Polymerization
  • Oxidation
  • Chlorination

What property of a cross-linked polymer allows it to return to its original form when released?

  • Stretch ability
  • Presence of cross-links (correct)
  • High reactivity
  • Loose coiling

In chain polymerization, what is the role of free radicals?

  • Cause polymer discoloration
  • Increase polymer stiffness
  • Initiate polymer degradation
  • Promote chain growth (correct)

What is a defining characteristic of free radicals in chain polymerization?

<p>Short life span (B)</p> Signup and view all the answers

Which stage of chain polymerization involves the addition of one of the free radicals to a monomer molecule?

<p>Propagation (B)</p> Signup and view all the answers

What angles do carbon-carbon single bonds rotate to make in a polymer chain?

<p>$109^{ ext{o}}$ (D)</p> Signup and view all the answers

Which type of copolymer has a truly random distribution of repeat units?

<p>Random Copolymers (D)</p> Signup and view all the answers

What distinguishes the crystalline property of polymer molecules from other crystalline solids?

<p>Semi-crystallinity (C)</p> Signup and view all the answers

In polymer science, what is the main factor that determines the physical and mechanical properties of a semi-crystalline polymer?

<p>Crystallinity degree and crystallite arrangement (C)</p> Signup and view all the answers

Which type of copolymer exhibits branched polymers with branches having a different chemical structure than the main chain?

<p>Graft Copolymers (C)</p> Signup and view all the answers

What is the technological importance of the crystallization process in polymers?

<p>Affecting physical and mechanical properties (D)</p> Signup and view all the answers

How do crystalline solids differ from amorphous solids in terms of atomic arrangement?

<p>Regular three-dimensional arrays of atoms (B)</p> Signup and view all the answers

What is the molecular weight of the entire polymer chain if the degree of polymerization of an Ethylene polymer chain is 10,000?

<p>1,000,000 g/mol (D)</p> Signup and view all the answers

How many carbon atoms are present in the ethylene polymer chain with a degree of polymerization of 10,000?

<p>10,000 (C)</p> Signup and view all the answers

What does the number-average molar mass (Mn) represent in a polymer sample?

<p>The sum of each molecule's molar mass multiplied by its mole fraction (D)</p> Signup and view all the answers

In a molar mass distribution curve, what does Mw indicate?

<p>The average molar mass weighted by each molecule's mole fraction (B)</p> Signup and view all the answers

How is the number-average molar mass (Mn) calculated in a polymer sample?

<p>By summing the products of each molar mass and its mole fraction (B)</p> Signup and view all the answers

What is represented by the weight fraction in a polymer sample?

<p>The fraction of each molecule's contribution to total sample mass (A)</p> Signup and view all the answers

What are the molar masses of the two paraffins in the first example?

<p>142 g/mol and 2662 g/mol (C)</p> Signup and view all the answers

What is the number of moles present in the 2g specimen for the first blend?

<p>70.42<em>10^-4 mol and 3.76</em>10^-4 mol (B)</p> Signup and view all the answers

What are the average molar masses (Mn and Mw) of the first blend?

<p>Mn = 270 g/mol, Mw = 1402 g/mol (D)</p> Signup and view all the answers

What does Mn sensitivity depend on according to the examples?

<p>The mixture of molecules of low molecular mass (D)</p> Signup and view all the answers

What aspect affects Mw sensitivity according to the text?

<p>The mixture of molecules of high molecular mass (C)</p> Signup and view all the answers

Which blend had a higher difference between Mn and Mw in the examples?

<p>Blend with C1000H2002 (B)</p> Signup and view all the answers

Why does poly(vinyl chloride) have a higher Tg than polypropylene?

<p>Poly(vinyl chloride) has polar groups like -Cl, which restrict rotation more than non-polar groups. (C)</p> Signup and view all the answers

How does an increase in molar mass affect the glass transition temperature (Tg) of a polymer?

<p>Tg increases as the molar mass of the polymer is increased. (B)</p> Signup and view all the answers

What effect does a high density of branching have on the glass transition temperature (Tg) of a polymer?

<p>It raises Tg by restricting chain mobility. (B)</p> Signup and view all the answers

How does crosslinking affect the glass transition temperature (Tg) of a polymer?

<p>Crosslinking increases Tg by increasing the specific volume of the polymer. (A)</p> Signup and view all the answers

Which type of groups tend to raise the glass transition temperature (Tg) of a polymer?

<p>-OH groups (A)</p> Signup and view all the answers

How does polar interaction affect the glass transition temperature (Tg) of a polymer?

<p>Polar interactions raise Tg by restricting rotation further. (C)</p> Signup and view all the answers

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