marquez (ecm739) – H11: Thermo 1 – McCord – (53110)
1
This printout should have 29 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
On January 1, 2001, a bookstore had 266,478
books in stock. On ±ebruary 1, 2001, the same
bookstore had 257,814 books in stock. What
is the value oF Δ(books) For the bookstore
during that period?
Correct answer:

8664 books.
Explanation:
B
f
= 257
,
814 books
B
i
= 266
,
478 books
Δ
B
=
B
f

B
i
= 257
,
814 books

266
,
478 books
=

8664 books
Thus the bookstore had 8664 Fewer books
on ±ebruary 1.
002
10.0 points
Work is
1.
chaotic molecular motion.
2.
heat.
3.
organized molecular motion.
correct
4.
potential energy.
5.
kinetic energy.
Explanation:
Work is organized molecular motion since
it is displacement oF a solid against a Force.
003
10.0 points
A chemical reaction takes place in a container
oF crosssectional area 100 cm
2
. As a result oF
the reaction, a piston is pushed out through 12
cm against an external pressure oF 670 torr.
What is the value For
w
For this reaction?
(Sign does matter.)
Correct answer:

107 J.
Explanation:
004
10.0 points
A 100 W electric heater (1 W = 1 J
/
s) oper
ates For 7 min to heat the gas in a cylinder. At
the same time, the gas expands From 4 L to
12 L against a constant atmospheric pressure
oF 3
.
876 atm. What is the change in internal
energy oF the gas?
Correct answer: 38
.
8581 kJ.
Explanation:
P
ext
= 3
.
876 atm
V
ini
= 4 L
1 L
·
atm = 101
.
325 J
V
Fnal
= 12 L
IF the heater operates as rated, then the to
tal amount oF heat transFerred to the cylinder
will be
q
= (100 J
/
s) (7 min) (60 s
/
min)
= 42000 J = 42 kJ
Work will be given by
w
=

P
ext
Δ
V
in this case because it is an expansion against
a constant opposing pressure:
w
=

(3
.
876 atm) (12 L

4 L)
=

31
.
008 L
·
atm
Convert to kilojoules (kJ)
w
= (

31
.
008 L
·
atm)(101
.
325J
/
L
·
atm)
=

3141
.
89 J =

3
.
14189 kJ
The internal energy change is
Δ
U
=
q
+
w
= 42 kJ + (

3
.
14189 kJ)
= 38
.
8581 kJ
005
10.0 points
A system had 150 kJ oF work done on it and
its internal energy increased by 60 kJ. How
much energy did the system gain or lose as
heat?
1.
The system gained 90 kJ oF energy as
heat.
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2
2.
The system lost 210 kJ of energy as heat.
3.
The system gained 60 kJ of energy as
heat.
4.
The system gained 210 kJ of energy as
heat.
5.
The system lost 90 kJ of energy as heat.
correct
Explanation:
Δ
U
=
q
+
w
q
= Δ
U

w
= 60 kJ

(+150 kJ)
=

90 kJ
(Negative means the system lost energy as
heat.)
006
10.0 points
When 2.00 kJ of energy is transferred as heat
to nitrogen in a cylinder Ftted with a piston
at an external pressure of 2.00 atm, the nitro
gen gas expands from 2.00 to 5.00 L against
this constant pressure. What is Δ
U
for the
process?
1.
+2
.
61 kJ
2.
0
3.

0
.
608 kJ
4.

2
.
61 kJ
5.
+1
.
39 kJ
correct
Explanation:
q
= 2 kJ
P
= 2 atm
V
0
= 2 L
V
f
= 5 L
±or expansion against a constant external
pressure,
w
=

P
ext
Δ
V
= (

2 atm)(5 L

2 L)
×
(101
.
325 J
·
L
−
1
·
atm
−
1
)
=

607
.
95 J =

0
.
60795 kJ
.
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 Spring '07
 Holcombe
 Enthalpy, Energy, Standard enthalpy change of formation, kJ/mol, Marquez

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