Iype, Shelby – Homework 10 – Due: Nov 21 2007, 6:00 pm – Inst: Vandenbout
1
This
printout
should
have
25
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
The due time is Central
time.
001
(part 1 of 1) 10 points
On January 1, 2001, a bookstore had 266,478
books in stock. On February 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 February 1.
002
(part 1 of 1) 10 points
Work is
1.
chaotic molecular motion.
2.
organized molecular motion.
correct
3.
heat.
4.
kinetic energy.
5.
potential energy.
Explanation:
Work is organized molecular motion since
it is displacement of a solid against a force.
003
(part 1 of 1) 10 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 20
cm against an external pressure of 558 torr.
What is the value for
w
for this reaction?
(Sign does matter.)
Correct answer:

149 J.
Explanation:
004
(part 1 of 1) 10 points
A 100 W electric heater (1 W = 1 J
/
s) oper
ates for 14 min to heat the gas in a cylinder.
At the same time, the gas expands from 5 L to
12 L against a constant atmospheric pressure
of 4
.
332 atm. What is the change in internal
energy of the gas?
Correct answer: 80
.
9274 kJ.
Explanation:
P
ext
= 4
.
332 atm
V
ini
= 5 L
1 L
·
atm = 101
.
325 J
V
final
= 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) (14 min) (60 s
/
min)
= 84000 J = 84 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
=

(4
.
332 atm) (12 L

5 L)
=

30
.
324 L
·
atm
Convert to kilojoules (kJ)
w
= (

30
.
324 L
·
atm)(101
.
325J
/
L
·
atm)
=

3072
.
58 J =

3
.
07258 kJ
The internal energy change is
Δ
U
=
q
+
w
= 84 kJ + (

3
.
07258 kJ)
= 80
.
9274 kJ
005
(part 1 of 1) 10 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 60 kJ of energy as
heat.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Iype, Shelby – Homework 10 – Due: Nov 21 2007, 6:00 pm – Inst: Vandenbout
2
2.
The system lost 210 kJ of energy as heat.
3.
The system gained 210 kJ of energy as
heat.
4.
The system lost 90 kJ of energy as heat.
correct
5.
The system gained 90 kJ of energy as
heat.
Explanation:
006
(part 1 of 1) 10 points
When 2.00 kJ of energy is transferred as heat
to nitrogen in a cylinder fitted 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.
+1
.
39 kJ
correct
2.
0
3.
+2
.
61 kJ
4.

0
.
608 kJ
5.

2
.
61 kJ
Explanation:
007
(part 1 of 1) 10 points
A 1.00 g sample of
n
hexane (C
6
H
14
) under
goes complete combustion with excess O
2
in
a bomb calorimeter. The temperature of the
1502 g of water surrounding the bomb rises
from 22.64
◦
C to 29.30
◦
C. The heat capacity
of the calorimeter is 4042 J/
◦
C. What is Δ
U
for the combustion of
n
C
6
H
14
? One mole of
n
C
6
H
14
is 86.1 g. The specific heat of water
is 4.184 J
/
g
·
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '07
 Fakhreddine/Lyon
 Chemistry, Enthalpy, Energy, Heat, Iype

Click to edit the document details