Chem1120pretest2Summeri2016
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. When the system A + B
C + D is at equilibrium,
a. the forward reaction has stopped.
b. the reverse reaction has stopped.
c. both the forward and the reverse reactions have stopped.
d. neither the forward nor the reverse reaction has stopped.
e. the sum of the concentrations of A and B must equal the sum of the concentrations of C
and D.
____
2. Given the following reaction and its equilibrium constant at a certain temperature:
N2(g) + 3H2(g)
2NH3(g)
Kc = 3.6  108
Calculate the numerical value of the equilibrium constant for the following reaction at the same temperature.
NH3(g)
a.
b.
c.
d.
e.
____
N2(g) +
H2(g)
2.8  109
1.9  104
1.3  107
5.3  105
7.7  1018
3. Consider the gas phase system below at a high temperature. The form of the expression for the equilibrium
constant, Kc, ____.
4NH3 + 5O2
4NO + 6H2O
a. cannot be determined without rate data
b.
is
c.
is
d.
is
e.
is
____
4. For a reversible reaction with a one-step mechanism, A
B , the rate of the forward reaction is rate f = 3.2
6 1
 10 s [A] and the rate of the reverse reaction is rate r = 4.6  104 s1 [B]. What is the value of Kc for this
reaction?
a. 2.5  1011
b.
c.
d.
e.
7.0  109
7.0  103
1.4  102
1.5  109
____
5. Which of the following statements about the reaction quotient, Q, is false?
a. The value of Q can be used to predict equilibrium concentrations.
b. It has the same expression as Kc.
c. Its value is calculated using nonequilibrium concentrations.
d. If Q > Kc, the reaction must move to equilibrium by forming more reactants.
e. If Q < Kc, the reaction must move to equilibrium by forming more products.
____
6. At equilibrium, the following amounts are found at a certain temperature in a 3.0-liter container: 2.0 mole of
Cl2, 0.80 mol of H2O (steam), 0.0030 mol of HCl, and 0.0045 mol of O2. Evaluate Kc at that temperature.
2Cl2(g) + 2H2O(g)
4HCl(g) + O2(g)
a.
b.
c.
d.
e.
____
4.7  1014
8.4  107
1.4  1013
2.2  1013
7.1  1012
7. The equilibrium constant for the following gas phase reaction is 0.50 at 600C. A mixture of HCHO, H2, and
CO is introduced into a flask at 600C. After a short time, analysis of a small amount of the reaction mixture
shows the concentrations to be [HCHO] = 1.5 M, [H2] = 0.5 M, and [CO] = 1.0 M. Which of the following
statements about this reaction mixture is true?
HCHO
H2 + CO
a. The reaction mixture is at equilibrium.
b. The reaction mixture is not at equilibrium, but no further reaction will occur.
c. The reaction mixture is not at equilibrium, but will move toward equilibrium by forming
more HCHO.
d. The reaction mixture is not at equilibrium, but will move toward equilibrium by using up
more HCHO.
e. The forward rate of this reaction is the same as the reverse rate.
____
8. The equilibrium constant, Kc, is 0.022 at 25C for the reaction below. What is the concentration of PCl 5 at
equilibrium if a reaction is initiated with 0.80 mole of PCl 5 in a 1.00-liter container?
PCl5(g)
PCl3(g) + Cl2(g)
a.
b.
c.
d.
e.
____
0.080 M
0.12 M
0.54 M
0.68 M
0.76 M
9. For the following system at equilibrium,
H2(g) + CO2(g)
H2O(g) + CO(g)
the addition of H2(g) would cause (according to LeChatelier's principle)
a. only more H2O(g) to form.
b.
c.
d.
e.
only more CO(g) to form.
more H2O(g) and CO(g) to form.
only more CO2(g) to form.
no change in amounts of products or reactants.
____ 10. Suppose we let the reaction below come to equilibrium. Then we decrease the total pressure, by increasing the
volume of the container. What will be the effect on the net amount of SO 3(g) present?
2SO2(g) + O2(g)
2SO3(g)
a.
b.
c.
d.
e.
It increases.
It decreases.
It does not change.
The question cannot be answered without knowing the value of K.
The question cannot be answered without knowing the value of H0.
____ 11. For the gas phase reaction below, H0 = 1.6  102 kJ for the forward reaction.
SO2 +
O2
SO3
In order to increase the yield of SO3, the reaction should be run
a. at high P, high T.
b. at high P, low T.
c. at low P, high T.
d. at low P, low T.
e. at high P, but is independent of T.
____ 12. Ammonium carbamate decomposes into NH3 and CO2 when heated.
NH4(NH2CO2)(s)
2NH3(g) + CO2(g)
If 25.0 g of ammonium carbamate is placed in an empty chamber and heated to 100C, what are the
equilibrium concentrations of NH3 and CO2? Kc = 58.3 at 100C.
a. [NH3] = 2.44 M; [CO2] = 4.88 M
b. [NH3] = 4.88 M; [CO2] = 2.44 M
c. [NH3] = 29.2 M; [CO2] = 14.6 M
d. [NH3] = 15.3 M; [CO2] = 7.64 M
e. [NH3] = 10.8 M; [CO2] = 5.40 M
____ 13. A Brønsted-Lowry acid is defined as a ____.
a. species that donates a proton
b. species that accepts a proton
c. species that accepts a share in an electron pair
d. species that makes available a share in an electron pair
e. species that produces H+ ions in aqueous solution
____ 14. For the following system, the equilibrium constant at 445C is 51.0. If a reaction is initiated with the
following initial concentrations, [H2] = 2.06  102 M, [I2] = 1.45  102 M, and [HI] = 0, what will be the
equilibrium concentration of HI?
H2(g) + I2(g)
2HI(g)
a. 1.8  102 M
b. 1.4  101 M
c. 2.7  101 M
d. 2.6  102 M
e. 3.7  103 M
____ 15. A reaction begins with 0.600 mole of A and 0.200 mole of B in a 2.00-L container at a certain temperature.
What will be the equilibrium concentration of C?
A(g) + B(g)
C(g)
Kc = 23.5
a.
b.
c.
d.
e.
0.0684 M
0.0200 M
0.044 M
0.0836 M
0.105 M
Chapter 18 Values
The following values will be useful for the problems in this chapter.
Acid
K
Substance or Species
K
HF
HNO2
CH3COOH
HOCl
HOBr
HOCN
HCN
H2SO4
Ka = 7.2  104
Ka = 4.5  104
Ka = 1.8  105
Ka = 3.5  108
Ka = 2.5  109
Ka = 3.5  104
Ka = 4.0  1010
Ka1 = very large
Ka2 = 1.2  102
Ka1 = 4.2  107
Ka2 = 4.8  1011
NH3
(CH3)3N
[Co(OH2)6]2+
[Fe(OH2)6]2+
[Fe(OH2)6]3+
[Be(OH2)4]2+
[Cu(OH2)4]2+
HBO2
(COOH)2
Kb = 1.8  105
Kb = 7.4  105
Ka = 5.0  1010
Ka = 3.0  1010
Ka = 4.0  103
Ka = 1.0  105
Ka = 1.0  108
Ka = 6.0  1010
Ka1 = 5.9  102
Ka2 = 6.4  105
Kb = 5.0  104
H2CO3
CH3NH2
____ 16. Of the following, which acids are weak acids?
I.
HBr
II.
HF
III.
HNO3
IV.
HNO2
V.
H2CO3
VI.
H3PO4
a.
b.
c.
d.
e.
I, II, and III
II, IV, V, and VI
I, II, and V
IV, V, and VI
another combination
____ 17. What is the concentration of H3O+ ions in a solution in which pH = 4.32?
a. 4.8  105 M
b. 6.2  104 M
c. 5.1  104 M
d. 8.6  105 M
e. 3.5  104 M
____ 18. What is the pH of 400. mL of solution containing 0.0112 gram of HNO3?
a. 4.15
b. 3.35
c. 10.65
d. 3.75
e. 2.95
____ 19. The pH of a 0.10 M solution of a monoprotic acid is 2.85. What is the value of the ionization constant of the
acid?
a. 6.3  105
b. 3.8  106
c. 2.0  105
d. 4.0  108
e. 7.2  106
____ 20. Calculate the pH of 0.10 M HCN solution. Ka = 4.0  1010
a. 6.75
b. 5.20
c. 8.42
d. 9.52
e. 10.4
____ 21. Assume that five weak acids, identified only by numbers (I, II, III, IV, and V), have the following ionization
constants.
Acid
I.
II.
III.
IV.
V.
Ionization Constant (Ka value)
1.0  103
3.0  105
2.6  107
4.0  109
7.3  1011
The anion of which acid is the weakest base?
a. I
b. II
c. III
d. IV
e. V
____ 22. What is the percent ionization for a 1.0  103 M solution of pyridine? Kb = 1.5  109
a. 0.12%
b. 1.6%
c. 2.8%
d. 0.045%
e. 0.67%
____ 23. Calculate the pH of a 0.050 M solution of hydroxylamine, NH2OH. Kb = 6.6  109
a.
b.
c.
d.
e.
9.91
9.48
9.26
10.56
8.61
____ 24. Which response list the species present in the highest concentration in a solution of 0.20 M H3PO4?
a. H3PO4, H2PO4, HPO42
b. H2PO4, HPO42, PO43
c. H3PO4, H3O+, OH
d. HPO42, PO43, OH
e. H3PO4, H2PO4, H3O+
____ 25. Which one of the following salts produces neutral solutions when it is dissolved in water?
a. NaCN
b. NaOCl
c. NaF
d. NaBr
e. NaCH3COO
____ 26. What is the value of the (base) hydrolysis constant for NaNO 2, sodium nitrite? Ka = 4.5  104 for HNO2.
a. 4.5  104
b. 2.2  1011
c. 4.5  1018
d. 4.5  1010
e. 2.1  109
____ 27. Calculate the pH of 0.10 M solution of NaBO2.
a. 9.84
b. 12.89
c. 10.48
d. 11.11
e. 2.89
____ 28. Which of the following relationships in incorrect? Assume 25C.
a. pH + pOH = 14.00
b. [OH] = 10pOH
c. pKW = log KW
d. [OH] [H3O+] = 1.0  1014
e. pH = log [H3O+]
____ 29. Calculate the concentrations of H3O+ and OH ions in a 0.25 M HClO4 solution.
a. [H3O+] = 0.25 M; [OH] = 0.25 M
b. [H3O+] = 0.25 M; [OH] = 4.0 M
c. [H3O+] = 0.25 M; [OH] = 4.0  1014 M
d. [H3O+] = 0.50 M; [OH] = 2.0  1014 M
e. [H3O+] = 1.0  107 M; [OH] = 1.0  107 M
____ 30. Calculate the pH of a solution in which [OH] = 2.50  104 M.
a. 0.40
b.
c.
d.
e.
3.60
3.60
10.40
13.60
____ 31. What is the pOH of a solution in which [H3O+] = 3.60  1010 M?
a. 8.56
b. 5.44
c. 9.44
d. 4.56
e. 4.32
____ 32. Which of the following statements about measurement of pH is incorrect?
a. The pH of a solution can be determined using a pH meter.
b. The pH of a solution can be determined by the indicator method.
c. A pH meter is more accurate than an indicator for determining the pH.
d. Many indicators are strong acids or strong bases.
e. Acid-base indicators have different colors in solutions of different pH.
____ 33. Consider calculations of [H3O+] in each of the following solutions. Do not go through the calculations. For
which calculation is it not reasonable to assume that "x" is much less than the initial concentration? The x
represents concentration ionized.
a. 0.20 M H2O2
Ka = 2.4  1012
b. 0.010 M HCN
Ka = 4.0  1010
c. 0.010 M H2S
Ka1 = 1.0  107, Ka2 = 1.0  1019
d. 1.00 M NH3
Kb = 1.8  105
e. 0.010 M (COOH)2 Ka1 = 5.9  102, Ka2 = 6.4  105
____ 34. Calculate the ionization constant for a weak acid, HA, that is 1.60% ionized in 0.0950 M solution.
a. 2.69  103
b. 3.77  102
c. 9.91  106
d. 1.63  102
e. 2.47  105
____ 35. The pH of a weak monoprotic acid (HA) is 3.75. If the ionization constant for this acid is 8.9  106, what is
the concentration of the weak acid?
a. 0.890 M
b. 5.05 M
c. 0.0500 M
d. 0.00355 M
e. 0.00712 M
____ 36. The pH of a 0.100 M solution of a weak acid, HA, is 3.50. Calculate the percent ionization of the acid in
0.100 M solution.
a. 0.016%
b. 0.078%
c. 0.32%
d. 0.68%
e. 1.6%
____ 37. The hypothetical weak acid H2A ionizes as shown below. Calculate the [HA] in 0.20 M H2A.
H2A
H+ + HA
Ka1 = 1.0  107

+
2
HA
H +A
Ka2 = 5.0  1011
a.
b.
c.
d.
e.
6.3  105 M
1.0  107 M
3.0  104 M
2.2  106 M
1.4  104 M
____ 38. When salts derived from ____ acids and ____ bases are dissolved in water, the resulting solution is always
acidic.
a. strong; strong
b. strong; weak
c. weak; strong
d. weak; weak
e. no way to determine without Ka and Kb
____ 39. When solid NH4NO3 is added to water, the pH ____.
a. remains at 7
b. becomes greater than 7
c. becomes less than 7
d. is independent of the amount dissolved
e. Can not be determined
Chapter 19 Values
The following equilibrium constants will be useful for the problems in this chapter.
Substance
HCO2H
HNO2
HOCl
HF
HCN
H2SO4
HOBr
Constant
Ka = 1.8  104
Ka = 4.5  104
Ka = 3.5  108
Ka = 7.2  104
Ka = 4.0  1010
K1 = very large
K2 = 1.2  102
Ka = 2.5  109
Substance
H2CO3
(COOH)2
CH3COOH
HOCN
C6H5NH2
NH3
____ 40. Which acid / base pair would produce an acidic equivalence point?
a. HCl / RbOH
b. HCl / NH3
c. CH3COOH / KOH
d. H2SO4 / Ca(OH)2
e. HNO3 / Ba(OH)2
Constant
K1 = 4.2  107
K2 = 4.8  1011
K1 = 5.9  102
K2 = 6.4  105
Ka = 1.8  105
Ka = 3.5  104
Kb = 4.2  1010
Kb = 1.8  105
Chem1120pretest2Summeri2016
Answer Section
MULTIPLE CHOICE
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D
PTS: 1
TOP: Chapter 17 Basic Concepts
D
PTS: 1
TOP: Variation of Kc with the Form of the Balanced Equation
E
PTS: 1
TOP: The Equilibrium Constant
C
PTS: 1
TOP: The Equilibrium Constant
A
PTS: 1
TOP: The Reaction Quotient
A
PTS: 1
TOP: The Equilibrium Constant
D
PTS: 1
TOP: The Reaction Quotient
D
PTS: 1
TOP: Uses of the Equilibrium Constant, Kc
C
PTS: 1
TOP: Disturbing a System in Equilibrium: Predictions
B
PTS: 1
TOP: Disturbing a System in Equilibrium: Predictions
B
PTS: 1
TOP: Disturbing a System in Equilibrium: Predictions
B
PTS: 1
TOP: Uses of the Equilibrium Constant, Kc
A
PTS: 1
TOP: The Brønsted-Lowry Theory
D
PTS: 1
TOP: Uses of the Equilibrium Constant, Kc
D
PTS: 1
DIF: Harder Question
Uses of the Equilibrium Constant, Kc
B
PTS: 1
TOP: Review of Strong Electrolytes
A
PTS: 1
TOP: The pH and pOH Scales
B
PTS: 1
TOP: The pH and pOH Scales
C
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
B
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
A
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
A
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
C
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
E
PTS: 1
TOP: Polyprotic Acids
D
PTS: 1
TOP: Salts of Strong Bases and Strong Acids
B
PTS: 1
TOP: Salts of Strong Bases and Weak Acids
D
PTS: 1
TOP: Salts of Strong Bases and Weak Acids
B
PTS: 1
TOP: The Autoionization of Water
C
PTS: 1
TOP: The Autoionization of Water
D
PTS: 1
TOP: The pH and pOH Scales
D
PTS: 1
TOP: The pH and pOH Scales
D
PTS: 1
TOP: The pH and pOH Scales
E
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
E
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
35. ANS:
TOP:
36. ANS:
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37. ANS:
38. ANS:
39. ANS:
40. ANS:
TOP:
D
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
C
PTS: 1
Ionization Constants for Weak Monoprotic Acids and Bases
E
PTS: 1
TOP: Polyprotic Acids
B
PTS: 1
TOP: Salts of Strong Bases and Weak Acids
C
PTS: 1
TOP: Salts of Strong Bases and Weak Acids
B
PTS: 1
Weak Acid/Strong Base and Weak Base/Strong Acid Titration Curves