INORGANIC MATERIALS

   

   Final Test             100 points                                      
   ................................... name

   

   1. a) (10 points) Consider coordination number of cations and anions in the following
   structure type compounds, fill the blank positions:

   

   +--------------------------------------------------------------------------------------------+
   |n:m = 1:1  |CN (a:b)  |n:m = 1:2    |CN (a:b)  |n:m = 1:3  |CN (a:b)  |n:m = 2:3  |CN (a:b) |
   |-----------+----------+-------------+----------+-----------+----------+-----------+---------|
   |           |          |             |          |           |          |           |         |
   |-----------+----------+-------------+----------+-----------+----------+-----------+---------|
   |NaCl       |          |CaF[2        |8:4       |ReO[3      |          |Al[2]O[3   |6:4      |
   |-----------+----------+-------------+----------+-----------+----------+-----------+---------|
   |CsCl       |          |]TiO[2]      |6:3       |]AlCl[3    |6:2       |]§§§§§     |§§§§§    |
   |-----------+----------+-------------+----------+-----------+----------+-----------+---------|
   |ZnS        |          |SiO[2] quartz|          |]§§§§§     |§§§§§     |§§§§§      |§§§§§    |
   |-----------+----------+-------------+----------+-----------+----------+-----------+---------|
   |NiAs       |6:6       |§§§§§        |§§§§§     |§§§§§      |§§§§§     |§§§§§      |§§§§§    |
   +--------------------------------------------------------------------------------------------+

   

   b) (10 points) Devise a general rule which links stoichiometric coefficients n, m in M[n]X[m]
   with coordination numbers a and b for cations and anions, respectively.

   

   

   

   

   2. (10 points) Zeolite-A (LTA) has a single peak in the ^29Si NMR spectrum (- 89 ppm) and has
   a Si/Al ratio of 1. Comment on these observations with respect to the Si and Al distribution
   and ordering.

   

   

   

   

   

   3. (20 points) Semiconductors of the 13/15 and 12/16 types frequently adopt the sphalerite
   (zinc blende) structure. Draw a unit cell of ZnS-blende and calculate the number of formula
   units in the unit cell.

   

   

   

   

   

   

   

   

   

   

   

   

   

   4. (10 points) Stishovite is a high-pressure modification of SiO[2] having the rutile
   structure. Should it have longer or shorter bond lengths then quartz?

   5. (10 points) Which of these polyhedra represent the coordination environment of a metal atom
   in

               a) copper


               b) magnesium

   

   

   6. The solid state reaction between CaO and SiO[2] is an important process in the cement and
   iron production (slag formation). Ca[2]SiO[4] is formed in the first step. Write chemical
   reactions taking place at the interfaces and calculate the Kirkendall ratio for this process

   a) (10 points) First, assume counter diffusion of Ca^2+ and Si^4+

   b) (20 points) The assumption a) is unrealistic, because the highly charged Si^4+ is very
   strongly bound to the oxide network and its diffusion coefficient is negligible. Suggest
   alternative diffusion process and calculate the Kirkendall ratio.