Solid Structures
I.
CHEMISTRY 362—Worksheet
April 1, 2016
The solid phase of elemental sodium is described as sodium atoms packed in a body-centered cubic
arrangement.
a) Making use of the cube provided, place atoms into and on it as O, and complete the unit cell for a bodycentered cubic lattice. How many atoms are in the unit cell of the bcc.
b) How does the body centered cubic packing differ from the simple cubic? I.e., what is the unit cell for the
simple cubic and how many atoms are in the unit cell of the simple cubic? Which is more space efficient?
c) Sodium’s neighbor in the periodic table, magnesium, adopts a hexagonal closest packed structure. The
density of one of these metals is 1.74 g/cc and that of the other is 0.97 g/cc. Which is which? Give a reason for
your choice.
II.
a) What is the formula of this copper/gold alloy? Show how you derive it.
b) Consider the two structures shown below that are the unit cells for diamond and for zinc blende,
respectively. Calculate the number of carbon atoms in the unit cell of diamond. Show how you arrive at
the answer. Calculate the number of zinc and sulfur ions in the unit cell of zinc blende. Show how you
arrive at your answer.
CHEM 362 – worksheet
III.
Consider the Born-Haber cycle below.
A. Label each arrow with the appropriate thermodynamic process given below.
pg. 2
B. Using the data provided for M = lithium and X2 = fluorine, calculate the heat of formation for LiF (s).
a) Lattice enthalpy change or Lattice Energy
= - 1239 kJ/mol
b) Electron affinity enthalpy
= - 328 kJ/mol
c) Ionization energy
= + 531 kJ/mol
d) Bond dissociation Energy (1/2 F2 → F (g)) = + 79 kJ/mol
e) Atomization or Sublimation Energy
= + 161 kJ/mol
f) Standard Enthalpy of Formation
= ???? kJ/mol
C. Do you expect the Standard Enthalpy of formation of CsF to be greater or less than that of LiF. Discuss
what terms influenced your conclusion.