Practice Questions for Exam 1
CH 1020 Spring 2017
1. Which of the following arrangements of gas
particles would have the greatest entropy?
5. The normal freezing point of sulfur dioxide is 72 C.
For the process, SO2(l) → SO2(s) at 80 C, the signs of
ΔSuniverse, ΔSsystem and ΔSsurroundings would be:
A.
A.
B.
C.
D.
E.
B.
ΔSuniverse ΔSsystem



+
+
+
+

+
+
Ssurroudings
+

+
+

C.
6. A change of state releases 64.0 kJ of heat to the
surroundings at a constant pressure and a constant
temperature of 300 K. Calculate ∆Ssurr for this process.
D.
7. Using the values below, calculate Srxn for the
reaction:
Hg2+(aq) + 2Cl(aq)  HgCl2(s)
2. Which of the following would be expected to
have the lowest standard molar entropy, So
A. C8H18(l)
B. C12H26(s)
C. C8H18(s)
D. C12H26(l)
3. For which of the following processes would
∆So be expected to be most positive?
A. O2(g) + 2H2(g) → 2H2O(g)
B. H2O(l)→ H2O(s)
C. NH3(g) + HCl(g)→ NH4Cl(s)
D. 2NH4NO3(s) →
2N2(g) + O2(g) + 4H2O(g)
E. N2O4(g) → 2NO2(g)
4. What is the entropy criterion for spontaneous
change in an isolated system (exchanges
neither matter nor energy with the
surroundings)?
A.
B.
C.
D.
E.
Ssys > 0
Ssurr < 0
Stot < 0
Ssurr > 0
Ssys < 0
Hg2+(aq)
Cl(aq)
HgCl2(s)
S (J/Kmol)
32.2
56.5
146
8. Which of the following is not true?
A. A spontaneous reaction need not occur immediately.
B. A spontaneous reaction must be exothermic and
must have an increase in entropy.
C. The reverse of a nonspontaneous reaction is always
spontaneous.
D. A spontaneous reaction is one that can proceed on
its own.
9. The normal freezing point of sulfur dioxide is 72 C.
For the process, SO2(l) → SO2(s) at 80 C, the signs of
ΔH, ΔS, and ΔG would be:
ΔH
ΔS
ΔG
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10. Using the values below, calculate Grxn for
the reaction below at 25 C.
Hg2+(aq) + 2Cl(aq)  HgCl2(s)
Hf (kJ/mol) S (J/Kmol)
Hg2+(aq)
+171.1
32.2

56.5
Cl (aq)
167.2
HgCl2(s)
146
224.0
11. What can be said about the spontaneity of the
dimerization of sulfur in the gas phase?
2S(g)  S2(g)
S(g)
S2(g)
Hf kJ/mol
277
129
S J/(mol•K)
238
80.
A. The formation of S2(g) (forward reaction)
is spontaneous at all temperatures.
B. The formation of S(g) (reverse reaction)
is spontaneous at all temperatures.
C. The formation of S2(g) (forward reaction)
is spontaneous at low temperatures and
the formation of S(g) (reverse reaction) is
spontaneous at high temperatures.
D. The formation of S(g) (reverse reaction)
is spontaneous at low temperatures and
the formation of S2(g) (forward reaction)
is spontaneous at high temperatures.
12. What can you conclude about the spontaneity
of the following change?
13. Consider the dissolution of two substances, iodine, I2
and ammonia, NH3, in either benzene, C6H6, or
methanol, CH3OH. Which statement is correct?
A. Iodine is more soluble than ammonia in both
benzene and methanol.
B. Iodine is more soluble in benzene but ammonia is
more soluble in methanol.
C. Ammonia is more soluble in benzene but iodine is
more soluble in methanol.
D. Ammonia is more soluble than iodine in both
benzene and methanol.
14. Sodium iodide exhibits solubility in acetone. What is
the strongest solute-solvent interaction present?
acetone
A.
B.
C.
D.
E.
dispersion forces
ion-ion interactions
hydrogen bonding
dispersion forces
ion-dipole forces
15. What is the total ion concentration of an aqueous
solution that is 0.15 M Na2SO4?
16. Commercial cold packs often contain solid NH4NO3 and
a pouch of water. The temperature of the pack drops as
the NH4NO3 dissolves in water. Therefore, for the
dissolving of NH4NO3 in water,
A. ΔHsoln is negative and ΔSsoln may be negative or
positive.
B. ΔHsoln is negative and ΔSsoln is positive.
C. ΔHsoln is positive and ΔSsoln may be negative or
positive.
D. ΔHsoln is positive and ΔSsoln is positive.
A. The change is spontaneous at any
temperature.
B. The change is nonspontaneous at any
temperature.
C. The change is spontaneous above some
undefined temperature.
D. The change is spontaneous below some
undefined temperature.
E. We cannot know.
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17. Consider the formation of the three solutions
shown in the table. Rank the formation of the
solutions from most endothermic to most
exothermic.
Type of interaction
solute-solute
solvent-solvent
solute-solvent
A.
B.
C.
D.
E.
Strength of Interaction
Soln. I Soln. II Soln. III
strong weak
strong
strong weak
weak
weak strong
strong
exothermicity 
I < II < III
II < I < III
III < I < II
III < II < I
I < III < II
18. Assuming a solution density of 0.90 g/mL
which of the following 1 L solutions contains
the smallest amount of dissolved ammonia?
A. 15 M NH3
B. 25 m NH3
C. 28% NH3
19. Which of the following increases the
solubility of a gas in a given solvent?
A.
B.
C.
D.
E.
21. Use the solubility curve for sodium nitrite, NaNO2, to
answer the following question. A solution is prepared
by dissolving 60 kg of sodium nitrite in 50 kg of water
at 80 C and the resulting solution is cooled to 30 C.
Which of the following is true?
increasing the partial pressure of the gas
increasing the temperature of the solvent
both A and B
decreasing the temperature of the solvent
both A and D
20. The vapor pressure of a pure liquid increases
as the…
I. temperature of the liquid increases.
II. volume of the liquid increases.
III. pressure of the atmosphere decreases.
A. I only
B. III only
C. I and II
A. The cooled solution is unsaturated.
B. 90 kg of sodium nitrate is contained in the cooled
solution.
C. 60 kg of sodium nitrate is contained in the cooled
solution.
D. 45 kg of sodium nitrate is contained in the cooled
solution.
E. The amount of solute in solution cannot be
determined.
22. Oxygen solubility in water is 0.00412 g/100 mL at
20 °C and 760 mm Hg. Calculate the solubility of
oxygen gas in water at 20 °C and a pressure of
1150 mm Hg.
23. What phase(s) exists at point A in the phase diagram
below?
A
D. I and III
E. I, II and III
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24. Consider a substance with the following
characteristics.
 normal melting point 50 C
 normal boiling point 130 C
 triple point at 10 C and 0.1 atm
 critical point at 170 C and 20 atm
The substance, (i) initially at 0 C and 0.5
atm, is (ii) heated to 165 C and then (iii) the
pressure is increased to 25 atm. In what
phase does the substance exist after each
step? (Hint: Complete the phase diagram
below.)
27. A beaker of pure water and a beaker of an aqueous
glucose solution, C6H12O6, are placed in a sealed
chamber as shown below. What will happen to the
levels of the two solutions over time?
A.
B.
C.
D.
The levels of both liquids will decrease.
The levels of both liquids will increase.
The levels of the two liquids will remain the same.
The level of the solution will decrease, while the
level of the pure water will increase.
E. The level of the pure water will decrease, while the
level of the solution will increase.
28. What is the freezing point of a solution prepared from
50.0 g ethylene glycol (C2H6O2, non-volatile solute) and
85.0 g H2O?
29. Which of the following aqueous solutions would have
the largest freezing point depression?
A.
B.
C.
D.
E.
solid → gas → liquid
liquid → gas → supercritical fluid
solid → liquid → gas
gas → gas → liquid
solid → liquid → gas
25. Assuming the following substances all cost
the same per mole, which one would be most
cost effective as a way to lower the freezing
point of water? (Assume complete
dissociation)
A. HOCH2CH2OH
B. NaCl
C. MgCl2
D. KCl
26. A solution is prepared by dissolving 101.0 g
C12H22O11 in 500.0 g of water at 100 C. What
is the vapor pressure of the solution if the
vapor pressure of water at 100 C is
760 mm Hg?
A.
B.
C.
D.
0.200 m C12H22O11
0.100 m NH4NO3
0.150 m K2SO4
0.150 m NaCl
30. A cucumber is placed in a concentrated brine (sodium
chloride) solution. What will most likely happen?
A.
B.
C.
D.
E.
Water will flow from the cucumber to the solution.
Water will flow from the solution to the cucumber.
Salt will flow into the cucumber.
Salt will precipitate out.
No change will occur.
31. A solution exerts an osmotic pressure of 13.8 atm at
35 C. The solute has a van’t Hoff factor of 1.85. What
is the concentration of the solution?
32. What is the molar mass of an aromatic hydrocarbon if
0.85 g of it depresses the freezing point of 100.0 g of
benzene by 0.47 C?
33. A solution is prepared by adding 5.0 moles of LiNO3to
50.0 mole of water at 25 °C. Pure water has a vapor
pressure of 24.0 torr at this temperature. What is the
vapor pressure of the solution?
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34. Changing which of the following would cause
the rate of reaction to change?
I. temperature of reaction
II. concentration of a product
III. concentration of a reactant
37. Consider the decomposition of hydrogen peroxide.
2H2O2(l) → 2H2O(l) + O2(g)
If the concentration drops from 0.315 M at 0.1 h
(Point I) to 0.215 M at 5.9 h (Point II) what is the
average rate of the reaction?
35. What is the average rate of concentration
change for ammonia, NH3, if the average rate
of concentration change [H2]/t, is 1.5 x
10-3 M/s for the reaction below?
N2(g) + 3 H2(g) → 2 NH3(g)
36. A plot of product concentration as function of
time is represented below. The slope of line I
provides an __________ rate of reaction and
the slope of line II provides an
_____________ rate of reaction.
38. The oxidation of Br by BrO3 in acidic solution is
described by the equation
5Br(aq) + BrO3(aq) + 6H+(aq) 
3Br2(aq) + 3H2O(l)
The reaction is first order in Br, first order in BrO3 and
second order in H+.
What is the overall reaction order?
39. Write the rate law for the reaction in the previous
question assuming that time is measured in seconds.
40. What are the units of the rate constant, k, in the rate
law?
41. How does the reaction rate change if the H+
concentration is changed from 0.10 M to 0.05 M?
42. Given the following rate law, by what factor will the
rate increase by if the concentration of A is doubled and
the concentration of B is doubled?
Rate = k[A]3[B]0
Page 5 of 7
Use the initial rate data to answer the next two
questions, which refer to the following reaction.
48. What is the half-life of the following first order
reaction?
2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g)
Exp.
[NO]
[H2]
1
2
3
0.0420 M
0.0210 M
0.0210 M
0.0122 M
0.0122 M
0.0244 M
Initial rate
(M/s)
1.24  10−4
3.10  10−5
6.20  10−5
43. What is the rate law for this reaction? Be sure
to include a rate constant.
44. What would be the initial rate of reaction if
the initial concentration of NO is 0.310 M and
that of H2 is 0.515 M?
45. Which of the graphs below shows the correct
relationship for a first order reaction?
ln [B]
t = 0 min
min
t = 30 min
minmin
49. A second order reaction with an initial concentration of
1.5 M has a half-life of 100 minutes. How long is the
half-life of the reaction if the initial concentration is
0.75 M?
50. The diagrams below represent the starting
concentrations of reactants for a reaction. The initial
rates of I, II and III are 1: 3: 9, respectively. What rate
do you predict for IV?
1/[B]
time
time
Graph 1
Graph 2
1/[B]
ln [B]
time
Graph 3
A. Graph 1
B. Graph 2
time
Graph 4
C. Graph 3
D. Graph 4
46. Consider the 2nd order below which has a
rate constant of 0.541 M−1s−1. How long
will it take for the concentration of NO2 to
decrease from 0.872 M to 0.198 M?
2NO2(g) → 2NO(g) + O2(g)
47. The first order decomposition of N2O at
1000 K has a rate constant of 0.76 s1. If the
initial concentration of N2O is 10.9 M, what
concentration has been consumed after 2.5 s?
Page 6 of 7
USEFUL INFORMATION
H system
G = H  TS
Ssurroundings = -
Ho = npHof (products) - nrHof (reactants)
So = npSo (products) - nrSo (reactants)
T
Go = npGof (products) - nrGof (reactants)
Tb = i Kb  m
For water: Kb = 0.51 C/m
Tf = i  Kf  m
For water: Kf = 1.86 C/m
For benzene: Kf = 5.12 C/m
Psoln = Xsolvent  Psolvent
=iMRT
S = kH  P
760 torr = 1 atm
R = 8.314 J/K·mol = 0.08206 L·atm/ K·mol
[A]t = kt + [A]0
t½ =
[A]0
2k
ln [A]t = kt + ln[A]0
t½ =
ln 2
k
1/[A]t = kt + 1/[A]0
t½ =
1
[A]0 • k
Page 7 of 7