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</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</p> Signup and view all the answers

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

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

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

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

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

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

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

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

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

    <p>Blend with C1000H2002</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.</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.</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.</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.</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</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.</p> Signup and view all the answers

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