Do Super Heroes Need Villains

MAT 33 – Fall 2014                               Homework #3


Due:   9/15/’14

1. On the basis of ionic charge and ionic radii, predict crystal structures and coordination numbers for the following materials:
      a) MnS
      b) MgO
      c) CsI
      Justify your selections.

2. Would you expect CaO to have the cesium chloride, sodium chloride or zinc blende structure? Based on your answer, determine
  a)   the structure
  b)   the lattice parameter
  c)   the theoretical density
  d)   the packing factor.


3. For AgBr ceramics structure, sketch the closest packed plane and draw the closest packed direction. In the sketch, ionic species need to be distinguished.

4. The following table lists molecular weight data for a polyvinyl chloride (PVC) material.   Compute (a) the number-average molecular weight, (b) the weight-average molecular weight, (c) the unit molecular weight and (d) the degree of polymerization..

|Molecular Weight                         |xi                         |wi                         |
|Range g/mol                             |                           |                           |
|15,000–30,000                           |0.04                       |0.01                       |
|30,000–45,000                           |0.07                       |0.04                       |
|45,000–60,000                           |0.16                       |0.11                       |
|60,000–75,000                           |0.26                       |0.24                       |
|75,000–90,000                           |0.24                       |0.27                       |
|90,000–105,000                           |0.12                       |0.16                       |
|105,000–120,000                         |0.08                       |0.12                       |
|120,000–135,000                         |0.03                       |0.05                       |




5. The number average weight of a poly(ethylene-styrene)...