CHE132
Midterm 1
Form 0
1
CHE132
Midterm 1
Spring 2006
Form 0
There are 20 multiple choice questions.
Each question is worth 5 points.
The entire
exam is worth 100 points.
Constants
The Gas constant = R = 8.314 J mol
1
K
1
= 0.08206 L atm mol
1
K
1
The molar heat capacity of water is 75.291 J mol
1
K
1
.
The specific heat capacity of water is 4.184 J g
1
°C
1
The molar mass of water is 18.02 g mol
1
The density of liquid water is 1 g/mL.
1 atm = 1.013 x 10
5
Pa.
1 cm
3
= 1 x10
3
L = 1 x 10
6
m
3
1 cal = 4.184 J
Equations
E
sys
= q
sys
+ w
sys
H = q
p
w
sys
= P
ext
V
q = nC
T
H°
reaction
=
coeff
p
H°
f
(products) 
coeff
r
H°
f
(reactants)
S = q
T
/T
G° =
H°  T
S°
G
reaction,T
H°
reaction,298K
 T
S°
reaction,298K
S
(P
1 atm)
= S
 RlnP
S
(c
1 M)
= S
 Rlnc
G
reaction
=
G°
reaction
+ RTlnQ
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentCHE132
Midterm 1
Form 0
2
Question 1.
A 20 g piece of iron with T = 300 °C is placed in 250 mL of water in a glass beaker with
T = 30 °C.
What is the final temperature of the water and iron at thermal equilibrium
assuming that q
water
= q
iron
? The specific heat capacity of iron is 0.451 J g
1
°C
1
.
A: 270°C
B: 330°C
C: 32.31°C
D: 27.65°C
E: 165°C
m
iron
c
iron
(T
final
– 300) = m
water
c
water
(T
final
– 30)
20x0.451(T
final
– 300) = 250x4.184(T
final
– 30)
9.02T
final
+ 2706 = 1046T
final
– 31380
34086 = 1055.02T
final
so
T
final
= 32.31 °C
Question 2.
A 40g sample of water cools from 50
C to 30
C. During this process, 7,420 J of heat are
transferred from the water to the surroundings. Calculate the change in energy per mole
of the water (
E
water
) given that the volume of water is constant during this process.
A: 7.5 kJ/mol
B: 3.34 kJ/mol
C: 1.51 kJ/mol
D: The answer cannot be calculated since we do not know the expansion work done by
the water.
E: 3.36 kJ/mol
q
water
= 7420 J,
Moles of water = 2.22.
V = 0, so
E
water
= q
water
/ 2.22 =  3.34 kJ/mol
Question 3
Which one of the following statements is not
correct:
A: A phase change can be exothermic or endothermic.
B: The enthalpy change for a chemical reaction (
H) is equal to the heat transferred at
constant pressure (q
p
).
C: Exothermic reactions are always spontaneous.
D: If the volume of an ideal gas at constant temperature increases by a factor of 2 then
the pressure of the gas will decrease by a factor of 2.
E: The combustion of octane is an exothermic reaction.
Question 4
Which one of the following statements is not
correct:
A: In an open system, both matter and energy can be transferred from the system to the
surroundings.
B: In a closed system, energy but not matter can be transferred from the system to the
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '08
 Kerber
 Chemistry, Thermodynamics, Reaction, following statements, kJ mol1, G°

Click to edit the document details