HW 3 Inorganic Materials
Chemistry
Name:
Points: C7780 Date due: Dec. 21, 2016
Max. 100 points Fall 2016
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, 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. (50 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.
3. (20 pts.) Ferromagnetic magnetite can be crystallized by a vapor transport reaction under
atmosphere of HCl(g) as a transport agent. Powder of Fe3O4 reacts with HCl at hotter end and
crystallizes at cooler end.
a) Write and balance the VPT reaction:
Fe3O4(s) + HCl (g) ⇄
b) Is the reaction endo- or exothermic?
Atmosphere HCl(g)Fe3
O4
(s)
1270 K 1020 K