Chemistry 112
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Practice Exam 2A
Section
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IMPORTANT: On the scantron (answer sheet), you MUST clearly fill your name, your student
number, section number, and test form (white cover = test form A; yellow cover = test form
B). Use a #2 pencil.
There are 25 questions on this exam. Check that you have done all of the problems and filled in
the first 25 bubbles on the scantron. The maximum score on this exam is 25 points. Your score
will be reported in percent (max 100%).
Exam policy
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Calculators with text-programmable memory are not allowed.
Relevant data and formulas, including the periodic table, are attached at the end of this
exam.
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your scantron after the time is called.
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As you read the question, underline or circle key words to highlight them for yourself.
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There is no penalty for guessing.
CHEMISTRY 112 EXAM 2
Practice Exam 2A
-------------------------------------------------------------------------------------------------------------------1) Which one of the following aqueous oxide solutions would have a pH below 7.0?
A) P2O5
B) Na2O
C) CaO
D) Fe2O3
E) H2O
-------------------------------------------------------------------------------------------------------------2) What is the pOH of a 0.15 M solution of hypochlorous acid, HClO at 25°C? (Ka of HClO is 3.5 x 10−8)
A) 4.14
B) 7.00
C) 5.44
D) 10.15
E) 9.86
-------------------------------------------------------------------------------------------------------------3) Which of the following is NOT a strong acid?
A) HCl
B) HClO3
C) H2SO4
D) H3PO4
E) HClO4
--------------------------------------------------------------------------------------------------------------
4) The following reaction was demonstrated in class:
Ba(OH)2 •8 H2O (s) + 2 NH4SCN (s) → Ba(SCN)2 (aq) + 2 NH3 (g) + 10 H2O (l)
In the demo, the two solid salts were combined in a beaker that was placed atop a puddle of water on a
wooden block. As the reaction occurred, the beaker froze to the block. Which of the following sets of
data accurately describes this reaction?
∆H rxn
∆S rxn
Spontaneous at:
A)
(–)
(+)
All Temperatures
B)
(+)
(+)
Low Temperatures
C)
(–)
(–)
Low Temperatures
D)
(–)
(+)
High Temperatures
E)
(+)
(+)
High Temperatures
-------------------------------------------------------------------------------------------------------------5) Calculate [Ag+] at 298K for the following reaction as written using the conditions listed below:
AgCl (s) → Ag+ (aq) + Cl– (aq)
[Cl¯] = 1.0 x 10–10 M
∆G = −58.496 kJ/mol
∆G° = +55.600 kJ/mol
A) 1.0 x 10–10 M
B) 1.0 M
C) 1.3 x 10–5 M
D) 7.9 x 10–8 M
E) There is no Ag+ (aq) in the solution.
-------------------------------------------------------------------------------------------------------------6) Which of the following is most likely to act as a Lewis base?
-------------------------------------------------------------------------------------------------------------7) Which one of the following salts, when dissolved in water, forms a basic aqueous solution?
A) NH4Cl
B) NaBr
C) KClO3
D) FeBr3
E) NaF
-------------------------------------------------------------------------------------------------------------8) What is the pH of a 500 mL solution of 0.10 M NH3 at 25°C? (Kb of NH3 = 1.8 x 10−5)
A) 11.3
B) 8.3
C) 13.0
D) 11.1
E) 2.7
-------------------------------------------------------------------------------------------------------------9) What is the conjugate acid of HPO42− ?
A) PO43−
B) PO42−
C) H2PO42−
D) H2PO4−
E) H3PO4
--------------------------------------------------------------------------------------------------------------
10) What is the concentration of HAsO42− in a 0.25M solution of arsenic acid (H3AsO4) if the pH of the
solution is 1.46 at 25°C?
For arsenic acid, Ka1 = 5.6 x 10−3, Ka2 = 1.0 x 10−7, Ka3 = 3.0 x 10−12
A) 5.6 x 10−3 M
B) 1.0 x 10−7 M
C) 3.0 x 10−12 M
D) 6.0 x 10−1 M
E) 7.1 x 10−5 M
-------------------------------------------------------------------------------------------------------------11) What is the pH of a 0.05 M solution of NaOCl at 25°C? (Ka of HOCl = 3.5 x 10−8)
A) 4.38
B) 9.62
C) 3.92
D) 10.08
E) 11.37
-------------------------------------------------------------------------------------------------------------12) Which ion below will produce the most basic solution when dissolved in water?
-------------------------------------------------------------------------------------------------------------13) Calculate the percent ionization in a 0.56 M aqueous solution of phenol (C6H5OH), if the pH is 5.07 at
25°C (Ka = 1.3 x 10−10).
A) 1.5 x 10−3 %
B) 1.1 x 10−1 %
C) 1.5 x 10−5 %
D) 2.5 %
E) 3.5 x 10−3 %
-------------------------------------------------------------------------------------------------------------14) Consider the combustion of propane in the reaction below, where ∆H°rxn = −393 kJ/mol and ∆S°rxn=
101 J/mol-K.
C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l)
A propane heater is quite an asset in Russia. What is the maximum amount of work produced by the
above combustion reaction on a typical day in Oymyakon, Russia, when the temperature is –50°C?
(Assume standard enthalpy and entropy don’t change appreciably with temperature.)
A) 4.66 x 103 kJ/mol
B) 3.88 x 102 kJ/mol
C) 2.29 x 104 kJ/mol
D) 3.70 x 102 kJ/mol
E) 4.15 x 102 kJ/mol
-------------------------------------------------------------------------------------------------------------15) How is the chemical species NH4+(aq) best described?
A) Weak acid
B) Strong acid
C) Amphoteric
D) Weak base
E) Negligible acid
-----------------------------------------------------------------------------------------------------------16) What would happen if 0.5 moles of NaClO2 (aq) were added to a 1 L solution of 0.5 M HClO2?
I.
II.
III.
[H+] would increase
pH would increase
[HClO2] would increase
IV.
[OH− ] would increase
A) II only
B) I and II only
C) II and IV only
D) II, III, and IV only
E) All of the above
-------------------------------------------------------------------------------------------------------------17) What is the hydronium ion concentration of water at 75°C if pKw = 12.70?
A) 1.0 x 10−7 M
B) 4.5 x 10−7 M
C) 2.0 x 10−13 M
D) 1.0 x 10−14 M
E) 3.5 x 10−5 M
-------------------------------------------------------------------------------------------------------------18) To prepare a solution for an important series of reactions, a chemist adds 500 mL of 1 M NaOH to
1000 mL of 1 M CH3COOH (Ka = 1.8 x 10−5). What is the pH of the resultant solution at 25°C?
A) 1.80
B) 4.74
C) 5.12
D) 6.80
E) 7.89
-------------------------------------------------------------------------------------------------------------19) A 34-year-old man presents at an emergency room with fatigue, nausea, headache, and low blood
pressure. Upon further examination, it is found that his blood concentration of H2CO3 is 2.4 mmol/L, and
the concentration of HCO3− in his blood is 22 mmol/L. What is the pH of his blood? (Ka1 of H2CO3 = 4.3
x 10−7)
A) 6.37
B) 5.41
C) 7.33
D) 7.41
E) 7.12
-------------------------------------------------------------------------------------------------------------PLEASE USE THE FOLLOWING INFORMATION TO ANSWER THE NEXT 2 QUESTIONS:
A researcher performs a titration to determine the buffering capacity of a mixture of two solutions. The
researcher starts with 1 L of Solution A and performs a titration by adding Solution B and recording the
pH. The data are collected and plotted on a graph:
20) Which of the following best describes the identities of Solution A and Solution B?
A)
B)
C)
D)
E)
Solution A
Weak base
Strong acid
Strong acid
Weak acid
Weak acid
Solution B
Strong base
Weak base
Strong base
Strong acid
Strong base
-------------------------------------------------------------------------------------------------------------21) Approximately what volume of Solution B must be added to reach the half equivalence point of the
titration?
A) 250 mL
B) 450 mL
C) 800 mL
D) 900 mL
E) 1100 mL
-------------------------------------------------------------------------------------------------------------22) What is the pH of a 0.050 M solution of Ca(OH)2 at 25°C?
A) 1.0
B) 1.3
C) 12.7
D) 13.0
E) 13.5
-------------------------------------------------------------------------------------------------------------23) Calculate the Ka of a weak acid HA if a 0.19 M solution of HA has a pH of 4.52 at 25°C.
A) 6.5 x 10−9
B) 4.9 x 10−9
C) 1.8 x 10−5
D) 3.2 x 10−3
E) 2.1 x 10−8
-------------------------------------------------------------------------------------------------------------24) A titration enthusiast decides to titrate a 200 mL solution of 0.45 M benzoic acid (C6H5COOH) with
0.90 M NaOH. (Ka of benzoic acid is 6.5 x 10−5) What is the pH of the titrated solution at its equivalence
point at 25°C?
A) 8.92
B) 7.00
C) 4.14
D) 8.83
E) 5.17
-------------------------------------------------------------------------------------------------------------25) Given the following data, at what temperature does the Haber process (given by the reaction below)
become non-spontaneous? (Assume standard enthalpy and entropy do not change appreciably with
temperature.)
N2 (g) + 3 H2 (g) → 2 NH3 (g)
A)
B)
C)
D)
E)
∆Hf° (kJ/mol)
S° (J/mol-K)
N2 (g)
0
191.50
H2 (g)
0
130.59
NH3 (g)
−46.11
192.34
142°C
–51°C
191°C
25°C
This reaction is spontaneous at all temperatures
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------END OF EXAM
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ANSWER KEY:
1. A
2. E
3. D
4. E
5. A
6. C
7. E
8. D
9. D
10. B
11. D
12. E
13. A
14. E
15. A
16. D
17. B
18. B
19. C
20. E
21. B
22. D
23. B
24. D
25. C