HW 2 Inorganic Materials
Chemistry
Name:
Points: C7780 Date:
Max. 100 points Fall 2015 A
1. (15 pts) Give the stoichiometric formula for a compound possessing the unit cell below.
Atoms: red = O, silver = Cu (all Cu inside the unit cell).
2. (15 pts) Cu3N has the cubic anti-ReO3 structure, which is a rather open structure with Cu
atoms occupying.................... and the N atoms occupying.............................of the cubic unit
cell. It exhibits a large vacant site at ..........................of the cell which can be used for doping
with a metal and hence varying the electrical and optical properties.
a) Draw a unit cell of Cu3PdN.
b) Is this a primitive or centered cell?
c) What structure type it is?
3. (15 pts) Stishovite is a high-pressure modification of SiO2 having the rutile structure.
a) What is the coordination number of Si ..................and O....................?
b) Should it have higher or lower density then quartz?
c) Should it have longer or shorter SiO bond lengths then quartz?
d) Another phase of SiO2 at extremely high pressure was predicted to have a pyrite type
structure. Draw the unit cell. What is interesting about the oxygen bonding.
4. (15 pts) a) Write balanced chemical equation for a solid state reaction:
ZnC2O4 + Fe(OH)3  ZnFe2O4
b) What is the driving force in this reaction?
c) Cubic spinel ZnFe2O4 crystallizes with 8 formula units in the cubic unit cell. The cell
parameter a = 8.42 Ǻ. Calculate the density in g cm3
of the material.
NA = 6.022141 1023
mol1
, Ar(Zn) = 65.41, Ar(Fe) = 55.85, Ar(O) = 15,999.
5. (15 pts) The cell parameter for cubic spinel ZnFe2O4 is a = 8.42 Ǻ, for MnFe2O4 a = 8.50 Ǻ.
a) Suggest a reason for the difference.
b) What would be the cell parameter for the mixed-metal phase (MnxZn1x)Fe2O4 when x =
0.25, 0,50, and 0,75.
6. (10 pts) It has been predicted that transition metal oxides at high pressures will experience
so called “magnetic collapse”. Consider an octahedral coordination of the metal and based on
your knowledge of the ligand field theory suggest whether the high spin or the low spin
configuration of d electrons is more stable at high pressure?
7. (15 pts) Ferromagnetic magnetite can be crystallized by a vapor transport reaction under
atmosphere of HCl(g) as a transport agent. Powder of Fe3O4 reacts with HCl at hotter end and
crystallizes at cooler end.
a) Write and balance the VPT reaction:
Fe3O4(s) + HCl (g) ↔
b) Is the reaction endo- or exothermic? Explain.
Atmosphere HCl(g)Fe3
O4
(s)
1270 K 1020 K