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Solid State Chemistry
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Spring 2015
– Homework 5 –
Show all work (10 pts)
1. Transition metal oxides containing a metal ion with multiple oxidation states may be
non-stoichiometric. The non-stoichiometric compound may accommodate this by a
variety of ways, including cation vacancies, oxide ion (anion) vacancies, interstitial
cations, or interstitial anions. Soft chemistry techniques were used in the synthesis of
two compounds with the approximate composition of cobalt(IV) oxide, which has a
tetragonal unit cell containing one cobalt atom and two oxygen atoms. These were
characterized using powder X-ray diffraction, density measurements, and elemental
analysis. The unit cell is trigonal. The data are summarized in the table below.
Determine the most likely way in which the non-stoichiometry was accommodated
and support your justification.
Sample
1
2
O:Co ratio
2.00
1.92
Co:O ratio
0.50
0.52
Lattice parameters /Å
a = 2.8208, c = 4.2403
a = 2.8048, c = 4.2509
Density (g/cm3)
5.17
5.14
2. A possible defect cluster in Fe1-xO is given in the figure below.
a) Determine the vacancy:interstitialcy ratio for the cluster
b) Assuming this section is surrounded by Fe and O ions in octahedral sites as in the
Koch-Kohen cluster, determine the formula of the sample of a sample made
totally of such clusters.
c) Determine the numbers of Fe2+ and Fe3+ in octahedral sites.
3. Zeolite structures contains pores with different sizes. Download and open the
*.diamdoc files in the demo version 4.0.2 of Diamond by Crystal Impact
(http://www.crystalimpact.com/diamond/ ). Rotate the structure using the
botton.
Using the Measure Distances button
to determine the distances between atoms of
the pore entrance to determine the geometric minimum size of the pore opening.
1
File (Diamdoc)
Atom-atom distance in
pore opening
P-43n-Sodalite-zeolite
P63mmc-Gmelinite-zeolite
Pm-3m-Zeolite_A_Na12Al12Si12O48
FD3MZ-Faujasite_zeolite
4. Two metal oxide octahedra may share a corner, and edge, and/or a face. Sketch each
pair of connected octahedra. What is the formula (MxOy) of each pair of connected
octahedra?
a) corner-shared _______________
b) edge-shared _____________
c) face-shared _____________
5. The figure below shows a member of the homologous series WnO3n-1. It contains
WO6 octahedra that are corner and edge-sharing. Determine and outline the unit cell.
Determine the chemical formula. ____________
Determine the average oxidation state of the W._____________
6. Zeolite A has a single peak in the 29Si MAS NMR spectrum at 89 ppm and has a
Si/Al ratio of 1. Explain these observations.
7. Zeolite A (Ca form), when loaded with platinum, has been found to be a good catalyst
for the oxidation of hydrocarbon mixture. If the mixture contains branched chain
hydrocarbons, these do not react. Describe a possible reason to explain these
observations.
8. In the manganese(II) oxide the Mn2+ ions occupy the octahedral holes in the rock salt
structure.
a. Describe the splitting of the d-orbitals and assign symmetry labels.
b. Assuming the oxide ligand to be a weak field ligand (high spin), populate the
d orbitals.
c. The total spin of the Mn2+ is _________
d. Explain why the absorption lines due to transitions between the two 3d levels
are very weak for Mn2+.
2
9. The energy levels of Nd3+ in Y3Al5O12 that are involved in the laser action of the
crystal are shown in the following figure. Describe the processes that occur when the
laser is working.
10. Determine the ground state electron configuration for Nd3+. How many microstates
are possible for this electron configuration? What is the spin multiplicity? Determine
the term symbol for the ground state.
3