Explanation 020 part 1 of 1 10 points the vapor

Explanation:
020 (part 1 of 1) 10 points
The vapor pressure of water at 37
◦
C is 47.1
torr and its enthalpy of vaporization is 44.0
kJ · mol
- 1
. Estimate the vapor pressure of wa-
ter at 87
◦
C. Assume the enthalpy of vaporiza-
tion of water is independent of temperature.
1. 713 torr
2. 504 torr correct
3. 112 torr
4. 256 torr
5. 52 torr
Explanation:
021 (part 1 of 1) 10 points
Consider the temperature composition dia-
gram of a binary mixture of A and B which
forms a minimum boiling azeotrope: Initially
X
A
= 0 . 6.
0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0
0
20
40
60
80
100
120
140
X
A
boiling temperature (
◦
C)
Which of the following is true if the distil-
late is collected from a distillation apparatus
while the solution boils?
1. X
A
in the beaker will remain the same.
2. X
A
in the beaker will approach 0.
3. X
A
in the beaker will approach 1.
4. X
A
in the beaker will approach 0.3. cor-
rect
Explanation:
022 (part 1 of 1) 10 points
Mixing 17.6 kg of ethylene glycol (commercial
antifreeze, C
2
H
6
O
2
) with 6.00 gal of water
lowers the freezing point to - 10 . 0
◦
F. Suppose
you wanted to accomplish the same thing with
sugar (sucrose, C
12
H
22
O
11
) instead of ethy-
lene glycol. How many kilograms of sucrose
would you use? 1 gallon = 3.785 liters. K
f
for
water = 1 . 86
◦
C/m.
1. 3.09 kg
2. 97.1 kg correct

Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe 8
3. 4 . 68 × 10
- 3
kg
4. 17.6 kg
5. 6019 kg
Explanation:
023 (part 1 of 1) 10 points
Several interesting observations from the
world around you are listed below. Which
of these is NOT explained by a colligative
property?
1. Water boils at a higher temperature when
salt is added.
2. Antifreeze is added to a car radiator to
keep the car from overheating.
3. The freezing point of water is lowered
when salt is added.
4. A lobster will die when placed in fresh
water.
5. At high altitude it takes longer to cook
spaghetti. correct
Explanation:
Colligative properties of a solution depend
on the number of solute particles in solution,
not the type. Boiling point variations due
to pressure changes have nothing to do with
solutions and colligative properties (boiling
point variations due to particles in solution,
etc.).
024 (part 1 of 3) 10 points
Consider the following pressure diagram for a
binary liquid containing A and B.
0 1
x
A
70 torr
20 torr
If 8 mol of A and 8 mol of B are mixed,
what is the vapor pressure of B?
1. 20 torr
2. 35 torr correct
3. 45 torr
4. 10 torr
5. 70 torr
Explanation:
The mole fraction of A is
x
A
=
mol A
total mol
=
8 mol
8 mol + 8 mol
= 0 . 5 .
0 1
0 . 5
20 torr
35 torr
025 (part 2 of 3) 10 points
What is the corresponding vapor pressure of
A?
1. 35 torr
2. 10 torr correct
3. 20 torr
4. 45 torr

Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe 9
5. 70 torr
Explanation:
0
1
0 . 5
20 torr
10 torr
026 (part 3 of 3) 10 points
What is the corresponding total vapor pres-
sure?
1. 20 torr
2. 35 torr
3. 45 torr correct
4. 70 torr
5. 10 torr
Explanation:
0 1
0 . 5
20 torr
45 torr
027 (part 1 of 1) 10 points
Arrange H
2
O, NH
3
, Ar, and NaCl in order of
expected increasing boiling points.