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©2010 Sarah L. Keller
Homework Set #4
 Chem452
Note:
Midterm 1 will be Monday, Feb 1.
It will cover subjects only through homework 4, even though we
will continue ahead in class.
This is because I want you to practice problems before you see them on
exams.
Homework 4 answers will be posted at the usual time, but your work will not returned before the
exam, so keep a copy to study from.
The exam first page with equations is posted.
You are not allowed a
page of your own notes.
Also, to help you plan ahead, a short, halfhomework set is due Feb 4/5.

1)
Some equations are always true; others are true only under restricted conditions, such as at constant
volume, for adiabatic process only, for an ideal gas, for
PV
work only, and so on.
For each of the
following equations, state what are the minimum conditions sufficient to make them true. (Some
subscripts normally present have been omitted. You may assume that the system is uniform in properties:
T, P, E,
and so on are everywhere the same.)
This problem taken from Tinoco 2.16.
Hint: You do not
have to say whether each equation assumes only PV work.
.. almost all of them do. For example, if the
equation given is PV=nRT, you’d answer that the equation is valid only for an ideal gas.
a)
±
U
=
q
+
w
b)
q
=
±
H
c)
C
P
=
±
H
±
T
d)
±
H
=
±
U
+
±
(
nRT
)
e)
P
+
a
n
2
V
2
±
²
³
´
µ
¶
V
·
nb
()
=
nRT
f)
w
=
±
P
ext
²
V
2)
My friend Andrew speculates that many bad relationships could be avoided if everyone had a proper hot
water bottle  then nobody would be tempted to sleep with an inappropriate partner just to stay warm in
the winter.
(Andrew currently lives in Halifax).
a)
Assume that all of the 6000 kJ/day of a human’s basal metabolic rate are converted to heat and that
1/3 of this heat is lost during an 8 hour night.
Assume also that a hot water bottle holds 2L of water
at 50
˚
C that cools to 20
˚
C during the night.
Compare the
±
H.
(Answer: 1 human
±
8 water bottles.)
b)
The molar mass of ATP is 573.1 g/mol.
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 Winter '09
 robinson

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