CHEMISTRY 101
Hour Exam I
September 24, 2013
Adams/Lindquist
Name ______________________________
Signature ___________________________
Section _____________________________
“The most authentic thing about us is our capacity to create, to overcome, to endure, to transform, to love and to be greater than our suffering.” -­‐-­‐Ben Okri-­‐-­‐ This exam contains 17 questions on 8 numbered pages. Check now to make sure you
have a complete exam. You have one hour and fifteen minutes to complete the exam.
Determine the best answer to the first 15 questions and enter these on the special answer
sheet. Also, circle your responses in this exam booklet. Show all of your work and
provide complete answers to questions 16 and 17.
1-15
(30 pts.)
_________
16
(13 pts.)
_________
17
(17 pts.)
_________
(60 pts)
_________
Total
Useful Information:
Always assume ideal behavior for gases (unless explicitly told otherwise).
PV = nRT
K = °C + 273
R = 0.08206 L•atm/mol•K
1 L = 1.0567 qt
Avogadro’s number = 6.022 × 1023
1 m = 1.0936 yd
1 yd = 3 ft
1 mi = 1.6093 km
1 lb = 453.59 g
1 ft = 12 in
STP = standard temperature and pressure = 0°C and 1.00 atm
Assume atmospheric pressure is 1.00 atm (unless explicitly told otherwise).
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 1
Consider the following “microscopic” pictures to answer questions 1 through 3.
1.
(v)
(vi)
(i) only
(v) only
(ii) only
(i), (v)
(i), (ii), (v)
(i), (ii), (iii), (iv), (vi)
(ii), (iii), (vi)
(i) only
(i), (ii), (iv)
(vi) only
(ii) only
(iii) only
(ii), (iii)
(ii), (iii), (vi)
(iv), (vi)
How many grams of aluminum sulfate are in a 0.630 mole sample?
a)
5.
(iv)
Which picture(s) represent(s) a mixture of a gaseous element and a gaseous
compound?
a)
b)
c)
d)
e)
4.
(iii)
Which picture(s) represent(s) a mixture of two gaseous elements?
a)
b)
c)
d)
e)
3.
(ii)
Which picture(s) represent(s) a solid element?
a)
b)
c)
d)
e)
2.
(i)
77.5 g
b)
152 g
c)
172 g
d) 185 g
e) 216 g
If a 0.475-L sample of neon gas is heated from 27°C to 82°C at constant pressure,
what will be the volume of the sample at the higher temperature?
a)
0.401 L
b)
0.475 L
c)
0.562 L
d) 1.04 L
e) 1.44 L
CHEMISTRY 101
Hour Exam I
6.
Can a theory become a law? Choose the best answer.
a)
b)
c)
d)
e)
7.
100 – 200 mL
150 – 160 mL
158 – 159 mL
158.5 – 158.7 mL
158.59 – 158.61 mL
If the pressure on a 2.10 × 104 mL sample of gas is doubled at constant temperature,
what will be the new volume of the gas?
a)
b)
c)
d)
e)
9.
Yes. Once the experiment verifies the theory, it becomes a law. This is standard
practice when applying the scientific method.
Yes. Once the theory is refined and developed into a model, it can become a
law.
Yes. Even though it is already very difficult to change a theory, establishing it as
a law would give it more credibility and allow it to never be changed.
No. Theories are always developed at the end of the scientific method and laws
are developed at the beginning. Thus the two are not related to each other and
neither theories nor laws provide good explanations for experimental
observations.
No. A law is a summary of observed (measurable) behavior and a theory is an
explanation of behavior. A theory does not tell what happens, it attempts to
explain why it happens.
In lab you report a measured volume of 158.6 mL of water. Using significant figures
as a measure of the error, what range of answers does your reported volume imply?
Choose the best answer.
a)
b)
c)
d)
e)
8.
Fall 2013
Page No. 2
2.10 × 102 mL
1.05 × 104 mL
4.20 × 104 mL
2.10 × 108 mL
4.41 × 108 mL
Which of the following is(are) examples of a chemical change?
a)
b)
c)
d)
e)
A marshmallow turns black when toasted too long in a campfire.
When you use the perfume(cologne) your friend gave you for your birthday, the
liquid of the perfume evaporates quickly from your skin.
A rubber band stretches when you pull on it.
Ice on your sidewalk melts when you put table salt on it.
At least two of the above are examples of a chemical change.
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 3
10. How many of the following is(are) true regarding
I.
II.
III.
IV.
a)
37
Cl− and
40
Ar ?
same group number on the periodic table
same number of protons
same number of neutrons
same number of electrons
0
b)
1
c)
2
d) 3
e) 4
11. If a gaseous mixture is made of 3.50 g of He and 5.75 g of Ar in an evacuated 2.05-L
container at 25°C, what will be the partial pressure of Ar in the container?
a)
1.72 atm
b)
5.75 atm
c)
10.4 atm
d) 11.9 atm
e) 12.1 atm
-----------------------------------------------------------------------------------------------------------Consider the following scenario to answer questions 12 and 13.
A compound was analyzed and found to contain the following percentage of the elements
by mass: carbon, 79.89%; hydrogen, 20.11%.
12. Determine the empirical formula of the compound.
a)
CH
b)
CH2
c)
CH3
d) CH4
e) C7H20
13. Which of the following could be a molar mass of the compound analyzed above?
a) 13.018 g/mol
b) 16.042 g/mol
c) 28.052 g/mol
d) 30.068 g/mol
e) 104.23 g/mol
--------------------------------------------------------------------------------------------------------14. How many of the following statements is(are) true?
I.
II.
III.
A 1.00-liter bottle contains more soda than a 1.00-quart bottle.
A man who is 1.52 m tall is taller than a woman who is 5 ft 3 in. tall.
A 335-g container of peanut butter is heavier than a container holding a
½ pound.
IV. A bus moving at a speed of 45 mi/hr is traveling faster than a car
moving at 65 km/hr.
a)
0
b)
1
c)
2
d) 3
e) 4
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 4
15. If you have equal mole samples of each of the following compounds, which
compound contains the greatest number of oxygen atoms?
a)
b)
c)
d)
e)
magnesium nitrate
dinitrogen pentoxide
iron(III) phosphate
barium oxide
potassium acetate
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 5
Answer the questions below. Show all work! Only complete and coherent explanations
will receive full credit. Please limit your answers to the space provided.
16. a) For the measurement 0.003040 meters, indicate which (if any) zeros are
significant and which (if any) are not significant. Account for all five zeros in the
measurement and explain.
b) One molecule of a molecular element has a mass of 4.65 × 10–23 g. Provide the
chemical formula for this molecule. Show all work/justify your answer.
c) A substance AB2 is 69.55% B by mass. Calculate the percent A (by mass) for
A2B. Show all work. (Hint: First think about comparing the relative molar masses
of A and B using the percent mass given for AB2.)
(Continue on to #17 on the next page.)
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 6
17. An aluminum can contains a small amount of water and is boiled with the lid
removed. (See picture below.)
The heat is then turned off and the can sealed. Over time, the can crumples. (See
picture below.)
a) Why doesn’t the can explode or crumple when the water is heated to boiling with
the lid removed? In your explanation, be sure to include what is happening with
the gas molecules inside the can.
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 7
b) Why does the can crumple when the heat is turned off and the can is sealed? Use
the kinetic molecular theory to support your answer.
c) At the time the can is sealed and the heat turned off, the temperature and pressure
of the water vapor are 100.°C and 1.00 atm, respectively. The original volume of
the can is 4.00 L. Assuming the can is essentially “saturated” with water vapor (as
opposed to air) and the volume of the liquid water remaining in the can is
negligible, how many moles of water vapor is(are) in the can right when the can is
sealed?
(Continue on to the next page.)
CHEMISTRY 101
Hour Exam I
Fall 2013
Page No. 8
d) When the can is finished being crushed, it has an internal volume of 1.50 L. The
temperature of the gas is now 35°C and the pressure is again 1.00 atm (assuming
forces due to metal walls are negligible). How many grams of water condensed
from the time the can was sealed to completing its crushing process?