Professor Claude Lupis
July 1, 2002
3.025 Thermodynamics and Kinetics of Materials
Homework #1 - Due 7/3/2002
1.
a/ The EPA requires lead in air not to exceed 1.5 micrograms per m3 averaged
over 3 months. At room temperature, to what partial pressure of lead would that
requirement correspond?
b/ Estimate, through the Clausius-Clapeyron equation, the temperature
corresponding to that partial pressure.
Data: Pb melts at 600.6 oK and boils at 2023 oK with an entropy of vaporization
equal to 20.99 cal/oK.mol. The atomic weight of Pb is 207.2.
2.
Aluminum chloride AlCl3 reacts with oxygen according to the reaction:
2AlCl3 + 1.5 O2(g) = Al2O3 + 3Cl2(g)
o
a/ Calculate the H o298 and H1000
of that reaction as well as the heats of
formation of AlCl3 and Al2O3 at 1000oK.
b/ AlCl3 is reacted with air in a furnace at 1000oK. The amount of air is such that
the oxygen is in 10% excess of the stoichiometric requirement in the reaction
above. Calculate the heat required by the furnace per mole of alumina produced,
knowing that the input materials are provided at room temperature, the output
materials leave the furnace at 1000oK and that the heat losses to the surroundings
amount to 200 kJ/mol of alumina. Using the basis of one mole of alumina
product, draw a heat balance of the process at both 298 and 1000oK.
DATA:
o
H1000
 H o298 (kJ/mol):
Al
AlCl3
Al2O3
Cl2(g)
O2(g)
N2(g)
30.95
118.9
78.0
25.6
22.7
21.5
The heats of formation of AlCl3 and Al2O3 at 298oK are equal to –705.6 kJ/mol
and –1675.7 kJ/mol, respectively.
…
2
3.
Thallium Phase Diagram
Thallium exists in the following crystal structures: face centered cubic (), body
centered cubic () and hexagonal close-packed (). Estimate and plot (with
reasonable accuracy) the phase diagram for thallium. Do not include the vapor
phase.
DATA:
Transformation
Ho (J/mol)
So (J/oK.mol)
V o (cc/mol)
 l
4,142
7.179
0.39

377
0.744
-0.02

-320
0.17
0.10

60
0.92
0.08
At a pressure of 1 atm, the stable phases are:
: from 0oK to 507oK; : 507 to 577oK; l: 577 to 1744oK
The  structure is stable only at low temperatures and high pressures. Neglect the
effects of the thermal expansion and of the compressibility of the volumes of the
various phases.