Chemistry 162
Exam I
Student Name (Print): ___________________
February 18, 2015
RuID ___________________
The exam booklet has 25 questions for credit and one additional question to check the color of your
exam booklet. Please answer all 26 questions on the OpScan sheet. There is no penalty for guessing.
If you do not find the exact answer, bubble in the best choice. A proctor will check your picture ID,
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periodic table along with other useful data. The use of any other notes or information on this test or
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1. Sign your name across the top of the form.
2. Code the following information (blacken circles)
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Your EXAM FORM is 1
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Your EXAM FORM is 1
1
Consider the hypothetical reaction: 2A + 4B → C + 3D
Over an interval of 20.0 seconds, [B] is decreasing at an average rate of 0.0010 M s-1. In a
5.00 L container, how many moles of D will form in that 20.0 seconds interval?
A.
B.
C.
D.
E.
2
0.075 mol
0.050 mol
0.025 mol
0.015 mol
0.10 mol
A closed rigid container contains a saturated aqueous solution of nitrogen dissolved in the
water, and nitrogen in the gas phase. Which of the following would increase the
concentration of N2(g) in the solution?
X. Shake the container vigorously.
Y. Raise the temperature of the water.
Z. Add more N2(g) to the gas phase.
A.
B.
C.
D.
E.
3
X only
Y only
Z only
Y and Z only
X, Y, and Z
In which case would an ionic solid dissolve in water and release heat? Magnitude means
the value of ∆H without regard to sign (its “absolute value” in mathematical terms).
A. The magnitude of lattice energy is smaller than the magnitude of hydration energy.
B. The magnitude of lattice energy is larger than the magnitude of hydration energy.
C. The magnitude of lattice energy is larger than the magnitude of ion-dipole
attractions.
D. The magnitude of the ion-ion attractions is smaller than the magnitude of the dipoledipole attractions.
E. The magnitude of the dipole-dipole attractions is larger than the magnitude of the
dispersion attractions.
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4
Pure benzene, C6H6, freezes at 5.5 °C and boils at 80.1 °C (at 1 atm pressure).
For benzene, Kf = 5.12 °C/m and Kb = 2.53 °C/m
A solution of naphthalene, C10H8, dissolved in benzene has a freezing point of 1.50 °C.
What is the boiling point of this solution?
A.
B.
C.
D.
E.
5
A first-order reaction has a half-life of 120 seconds. What is the instantaneous rate of this
reaction when the concentration of the reactant is 0.50 M
A.
B.
C.
D.
E.
6
2.9 × 10-3 M s-1
6.2 × 10-4 M s-1
1.5 × 10-2 M s-1
1.8 × 10-4 M s-1
5.1 × 10-3 M s-1
3.5 g of a protein is dissolved in 150 mL of solution at 25 oC. The osmotic pressure of the
solution is 10.5 torr. Calculate the molar mass of the protein.
A.
B.
C.
D.
E.
7
82.1 °C
81.0 °C
80.4 °C
78.0 °C
83.4 °C
5800 g/mol
13,000 g/mol
23,000 g/mol
34,000 g/mol
41,000 g/mol
If a certain reaction has rate constant with units M-2 s-1, the overall order of the reaction is:
A.
B.
C.
D.
E.
0
1
2
3
4
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Given the following rate law, how does the rate of reaction change if both the
concentrations of X and Y are doubled?
Rate = k [X]2[Y]3
A.
B.
C.
D.
E.
9
The rate of reaction will increase by a factor of 2.
The rate of reaction will increase by a factor of 5.
The rate of reaction will increase by a factor of 9.
The rate of reaction will increase by a factor of 24.
The rate of reaction will increase by a factor of 32.
A liquid-liquid solution is called an ideal solution if:
W. It obeys PV = nRT
X. It obeys Raoult’s Law
Y. The solute-solvent interactions are similar in magnitude to the solute-solute
plus the solvent-solvent interactions.
Z. Solute-solute, solvent-solvent and solute-solvent interactions are very
different in magnitude.
A.
B.
C.
D.
E.
10
W, X, and Y
X only
X and Y only
X and Z only
Y only
SO2Cl2 decomposes in the gas phase according to the reaction:
SO2Cl2(g) → SO2(g) + Cl2(g)
The reaction is first order with k = 3.0 × 10-6 s-1
A rigid container has an initial pressure of 2.4 atm of SO2Cl2(g). What will be the total
pressure after 6.0 hours? (1 hour = 3600 s) Assume no change in temperature or volume
of the container.
A.
B.
C.
D.
E.
0.94 atm
2.25 atm
0.15 atm
2.55 atm
0.45 atm
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11
What is the activation energy for a reaction that triples its rate constant when the
temperature is increased from 20.0 °C to 40.0 °C?
A.
B.
C.
D.
E.
12
3.00 kJ/mol
41.9 kJ/mol
50.8 kJ/mol
60.7 kJ/mol
70.4 kJ/mol
Which of the following statements is characteristic of a first-order reaction?
X. If the reactant concentration doubles, the rate doubles.
Y. If the reactant concentration doubles, the half-life doubles.
Z. The time required for a reactant to decrease from 0.80 M to 0.60 M, is the
same as the time required for that reactant to decrease from 0.60 M to 0.45 M.
A.
B.
C.
D.
E.
13
X only
Y only
Z only
X and Z only
X and Y only
Which statements are true about elementary steps in a reaction mechanism:
X. Elementary steps cannot involve more than one chemical species.
Y. The rate law of an elementary step can be determined from its chemical
equation.
Z. Termolecular elementary steps are possible but rare.
A.
B.
C.
D.
E.
X only
Y only
Z only
Y and Z only
X, Y and Z
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14
Which of the following statements best describes the condition(s) for a successful
formation of a product according to the collision model?
A. The collision must involve a sufficient amount of kinetic energy to overcome the
activation energy.
B. The relative orientation of the particles has little or no effect on the formation of the
product.
C. The relative orientation of the particles has an effect only if the kinetic energy of the
particles is below some minimum value
D. The relative orientation of the particles must allow the formation of the product.
E. The collision must involve a sufficient amount of kinetic energy to overcome the
activation energy, and the relative orientation of the particles must allow for
formation of the product.
15
2H2O2(aq) → 2H2O(ℓ) + O2(g)
Reaction is first order
If 80.0% of a sample of H2O2(aq) reacts in 30.0 minutes, what is the half-life of this
reaction?
A.
B.
C.
D.
E.
16
12.9 minutes
8.68 minutes
10.3 minutes
16.7 minutes
14.1 minutes
Consider the following initial rate data for a hypothetical reaction between A and B
Experiment
1
2
3
Initial
[A]
0.0104
0.0312
0.0312
Initial
[B]
0.00400
0.00400
0.00200
The rate law for this reaction is:
A.
B.
C.
D.
E.
Rate = k[A][B]
Rate = k[A]2[B]
Rate = k[A][B]2
Rate = k[A]2
Rate = k[B]2
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Initial Rate (M s-1)
2.25 × 10-8
2.03 × 10-7
1.02 × 10-7
17
2C4H6(g) → C8H12(g)
Rate = k[C4H6]2
k = 0.0852 M-1 s-1
Starting with 0.0100 M C4H6, how long would it take for this concentration to decrease to
0.00700 M?
A.
B.
C.
D.
E.
18
232 s
503 s
126 s
742 s
417 s
The addition of a catalyst to a reaction would change which of the following?
X. Activation energy
Y. ∆H of the reaction
Z. Reaction mechanism
A.
B.
C.
D.
E.
19
A nitric acid solution is 70.0% by mass HNO3, and has a density of 1.42 g/mL. Calculate
the molarity of this solution.
A.
B.
C.
D.
E.
20
X only
X and Y only
Y and Z only
X and Z only
X, Y, and Z
0.60 M
6.8 M
1.60 M
12.4 M
15.8M
A solution of two volatile molecular compounds, A and B, shows negative deviation from
Raoult’s Law. This means that:
A.
B.
C.
D.
E.
The molecules of A interact strongly with other A molecules
The two liquids have a positive heat of solution.
Molecules of A interact weakly with molecules of B.
Molecules of A interact more strongly with B than A with A and B with B
Molecules of A hinder the strong interactions between B molecules
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21
Given the following proposed mechanism, predict the rate law for the overall reaction.
A2 + B2 → 2AB
Mechanism
A2 " 2A
A + B2 → AB + B
A + B → AB
A.
B.
C.
D.
E.
22
Rate = k[A2][B2]
Rate = k[A2][B2]2
Rate = k[A2][B2]½
Rate = k[A2]
Rate = k[A2]½[B2]
72 g
152 g
103 g
115 g
36 g
A certain reaction has an activation energy of 50 kJ/mol. At 290 K, approximately what
fraction of the molecules has enough energy to make it over the activation barrier upon
collision?
A.
B.
C.
D.
E.
24
fast
slow
fast
The vapor pressure of water at 25 °C is 23.8 torr. Determine the mass of glucose (molar
mass 180. g/mol) that must be added to 500.0 g of water to change the vapor pressure to
23.1 torr.
A.
B.
C.
D.
E.
23
(overall reaction)
1 in 103
1 in 106
1 in 109
1 in 1012
1 in 1015
At 25 oC, benzene has a vapor pressure of 95.1 torr and toluene has a vapor pressure of 28.4
torr. If a solution of benzene and toluene at the same temperature has a vapor pressure of
55.1 torr, what is the mole fraction of benzene is this solution?
A.
B.
C.
D.
E.
0.25
0.40
0.50
0.60
0.75
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25
0.152 moles of a solute is dissolved in 600. g of water. The freezing point of this solution
is -1.4 oC. Which one of the following is the solute?
Kf = 1.86 oC/m for water.
A.
B.
C.
D.
E.
26
C12H22O11
NaCl
MgCl2
FeCl3
Al2(SO4)3
What is the color of your exam?
A.
B.
C.
D.
White
Blue
Yellow
Pink
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