HW 2 Inorganic Materials
Chemistry
Name:
Points: C7780 Date:
Max. 100 points Fall 2013 A
1. (10 pts) In the crystalline Cu3N, copper atoms possess coordination number 2. What is the
coordination number of N?
2. (15 pts) X-ray radiation of a Cu anode ( = 1.54 Å) was diffracted under an angle of 14.22º
at silicon crystal. Calculate the interplanar distance d in Si for the first order diffraction (n =
1).
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?
4. (10 pts) Write balanced chemical equation for a solid state reaction:
ZnC2O4 + Fe(OH)3  ZnFe2O4
5. (20 pts) 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. (30 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.
m
V
V
SRT
G
ln
