HW 3 Inorganic Materials
Chemistry
Name:
Points: C7780 Date due:
Max. 100 points Fall 2018
1. (30 pts.) Use the ligand field theory to explain why Mn3O4 is a normal spinel while Fe3O4 is
an inverse spinel. Hint: draw diagrams of energy levels of d-electrons for ions in tetrahedral and
octahedral sites, use approximation ΔT = 4/9 ΔO for ligand field splitting energy, consider all
MO4 and MO6 moieties as high spin complexes, calculate ligand field stabilization energy in
terms of ΔO for both normal and inverse arrangement of ions, compare them and find which is
more stable.
2. (30 pts) Mixed metal oxides could be prepared by sol-gel reactions from aqueous solutions of
metal salts.
a) Order these ions Al3+
, Ba2+
, Cs+
, H+
, Li+
, Mg2+
according to the increasing value of
hydration enthalpy: Mz+
+ n H2O  [M(H2O)n]z+
Hhydration
b) For a hydrolytic reaction [M(H2O)N]z+
+ h H2O  [M(OH)h(H2O)N-h](z-h)+
+ h H3O+
Hº
= (75.2 – 9.6 z) kJ mol-1
and Sº
= (– 148.4 + 73.1 z) J K-1
mol-1
Write equation that gives a measure of spontaneity of reaction (= write a formula relating this
state function to Hº
and Sº
). Calculate, for which of the above listed ions is this reaction
spontaneous?
3. (40 pts.) Calculate the wall thickness of a hexagonal MCM-41 mesoporous material, assume
that it possesses cylindrical pores.
a) First, calculate the d(100) = interplanar distance in the (100) plane from the XRD
diffractogram. CuK radiation was used with  = 1.542 Å. Diffraction maximum was found at
2.14 °2.
b) Now, derive the formula relating the interplanar distance d(100) to the hexagonal mesoporous
parameter a0 and calculate its value.
c) Derive the formula relating the diameter Dp of a pore to specific surface area SA (870 m2
/g)
and total pore volume Vp (0.683 cm3
/g). Assume cylindrical pores.
d) Finally, calculate the wall thickness (wt) of MCM41 material.