HW 2 Inorganic Materials
Chemistry
Name:
Points: C7780 Date:
Max. 100 points Fall 2014 A
1. (15 pts) Assume that CaO reacts with CeO2 and forms CaCeO3.
a) What could be the structure type of this compound? ______________
b) Write balanced chemical equations for the reactions taking place at the interfaces (assume
counter diffusion of both cations) and calculate the Kirkendall ratio for this process.
I II
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.
CaO CaCeO3 CeO2
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.
6. (15 pts) Gibbs free energy change for nucleation GN is given by two terms – surface and
volume. GN = 4r2
SL + 4/3r3
GV
SL = the solid/liquid interfacial energy
ΔGV – the free energy change between the ‘monomer’ in solution and unit volume of bulk
crystal
S – supersaturation = the quotient (ratio) of the actual concentration and the concentration of
the respective species at equilibrium conditions, indicates how far away from equilibrium the
system is. Vm – molar volume of the bulk crystal, r – nucleus radius
a) Explain what is a critical radius of nuclei rC – draw a graph of GN versus r.
b) Suggest a way how to control the critical nucleation radius rC by changing some reaction
parameter.
7. (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?
m
V
V
SRT
G
ln

8. (15 pts) The binary phase FeSi can be crystallized by Vapor Phase Transport reactions with
iodine. The transport takes places (T1→T2) with deposition temperatures between T1 =
700 °C and T2 = 1030 °C.
a) Complete the balanced chemical equation:
FeSi (s) + I2 (g) 
b) Is the transport reaction of FeSi with iodine exothermic or endothermic?
c) Does this scheme correspond the transport reaction of FeSi? Why?