Chem 222
Problem Set 3
Intro to Inorganic Chemistry
Summer 2011
Friday, June 17, 2011
1. (box 6.4 H and S) List the coordination number of the cation, the coordination
geometry, the expected r+/r- range and the overall stoichiometry for CsCl and
CaF2
2. Calculate the the r+/r- for LiCl, NaBr, Na2O, What structure will each of these
adopt? Identify the elements on the appropriate lattice structure.
Chem 222
Intro to Inorganic Chemistry
Summer 2011
3. Estimate the ionic radius of Cs+. The lattice energy of CsCl is 633 kJ/mol. For
CsCl the Madelung constant, is 1.763 and the Born exponent is 10.7. The ionic
radius of Cl- is 1.81 Angstrom.
4. (H and S 6.15) Using data from the Appendices (of H and S) and the fact that
ΔfH° (298 K) = -859 kJmol-1, calculate a value for the lattice energy of BaCl2.
Outline any assumptions that you have made.
5. a) Give a balanced reaction for the burning of methanol in air.
b) Give two half reactions and the overall reaction for a direct methanol fuel cell
where the feed is methanol and water (methanol instead of H2 is used as a fuel
and a proton exchange membrane is still present)
6. Draw an MO diagram for the oxygen moiety in peroxide. Comment on the
magnetism.
7. Sulphur miners often have lung problems after a few years of working. Write
balanced reactions starting from S8 to account for this damage. Suggest a
compound that could be put in a respirator to mitigate this reaction.
8. (H and S, section 6.11) Sulphur and selenium have very similar redox activities.
For the following (unbalanced) sulphur chemistry, give the analogous reactions
for selenium and determine the oxidation state of the selenium in each compound.
[SO4]2- H2SO3SH2S
9. Draw the bonding and anti-bonding molecular orbitals arising py-py interactions
and pz-pz interactions.
10. (H&S 2.9) (a) Use MO theory to determine the bond order in each of [He2]+ and
[He2]2+.
(b) Does the MO picture of the bonding in these ions suggest that they
are viable species?
(c) Is either of these ions paramagnetic?
11. (H&S 2.25c) Account for the observation that, in the salt formed from the
reaction of Br2 and SbF5, the Br-Br bond distance in the Br2+ ion is 215 pm, i.e.
shorter than in Br2.
12. (H&S 15.20) Assuming that it has similar molecular orbital energies to those of
NO, use an MO approach to show the bonding in CO (ignore s-p mixing)
13. (RC&O 15.5) Contrast the behaviour of nitrogen and carbon by comparing the
properties of (a) methane and ammonia, and (b) ethene (ethylene) and hydrazine.
14. How are quartz glass and common soda-lime glass different?
15. (H and S, 6.6) What do you understand by the band theory of metals?
16. Chemical analysis of a germanium crystal reveals indium at a level of 0.0003
atomic percent.
Chem 222
Intro to Inorganic Chemistry
Summer 2011
a) Assuming the concentration of thermally excited charge carriers from the Ge
matrix is negligible, calculate the density of free charge carriers (carriers/cm3) in
this Ge crystal.
b) Draw a schematic energy band diagram for this material and label all crtical
features.
17. a) Aluminium Phosphide (AlP) is a semiconductor with a band gap Eg of 3.0 eV.
Sketch the absorption spectrum of this material (absorption vs. wavelength)
b) Aluminium antimonide (AlSb) is also a semiconductor. Do you expect the band
gap of this material to be greater or less than the bangap of AlP? Explain.
18. You wish to make n-type germanium.
a) Name a suitable dopant.
b) Name the majority charge carrier.
c) Draw a schematic energy band diagram of the doped material. Label the
valence band, conduction band and any energy levels associated with the
presence of the dopant.
19. (H&S 14.16a) Comment on the observation that the pyroxenes CaMgSi 2O6 and
CaFeSi2O6 are isomorphous.
Definitions/Concepts: glass, silica, silicates, silicone, molecular orbitals, -bond, πbond, nodal plane, bond order, , pnictogens, chalcogens, catenation,, fuel cell
hygroscopic, deliquescent, desiccant, dehydration, dehydrogenation, diamagnetism,
paramagnetism, ferromagnetism, allotrope, photosynthesis, amphoteric, basic oxide,
acidic oxide, orbital hybridization, n-type semiconductor, p-type semiconductor,
compound semiconductor, metal, metalloid, non metal, band theory.