Chemistry 112
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Practice Exam 2B
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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CHEMISTRY 112 EXAM 2
Practice Exam 2B
-------------------------------------------------------------------------------------------------------------------1. In the process below, which species are acting as Bronsted acids and bases?
OH–
H 2O
A.
acid
base
acid
base
B.
base
acid
base
acid
C.
acid
base
base
acid
D.
acid
acid
base
base
E.
base
acid
acid
base
----------------------------------------------------------------------------------------------------------2. ΔG° for the following reaction is −2879 kJ/mol. What is ΔGf° for glucose (C6H12O6)?
ΔGf° of CO2(g) is −394.4 kJ/mol and Δ Gf° of water is −237.2 kJ/mol
C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(l)
A. +275.4 kJ/mol
B. −479.8 kJ/mol
C. −910.6 kJ/mol
D. −2247 kJ/mol
E. +455.3 kJ/mol
ΔG°rxn = −2879 kJ/mol
----------------------------------------------------------------------------------------------------------3. A demonstration in class illustrated the acidity and basicity of various oxides. Which one of the
following oxides produces a basic solution when added to water?
A. SiO2
B. P4O10
C. Al2O3
D. Na2O
E. Cl2O7
----------------------------------------------------------------------------------------------------------4. Which of the following solutions would have a pH < 7?
i. NH4Cl (aq)
ii. CaF2 (aq)
iii. Al(NO3)3 (aq)
iv. HF (aq)
A. iv only
B. i and ii
C. ii and iii
D. i and iv
E. i, iii, and iv
----------------------------------------------------------------------------------------------------------5. What is the value of ΔG° for this reaction at 25 °C? Keq = 5.0 × 108
N2 (g) + 3 H2 (g)
A. +22 kJ/mol
B. –4.2 kJ/mol
C. –25 kJ/mol
D. –50 kJ/mol
E. –490 kJ/mol
2 NH3 (g)
----------------------------------------------------------------------------------------------------------6. The entropy of vaporization (ΔS°vap) for benzene is 96.4 J/K-mol. The enthalpy of vaporization
(ΔH°vap) is 33.9 kJ/mol. What is the boiling point of benzene?
A. 2.81°C
B. 0.353°C
C. 93.2°C
D. 4.8°C
E. 78.5°C
----------------------------------------------------------------------------------------------------------7. Solid ammonium nitrate (NH4NO3) is highly soluble in water. When it dissolves at 298 K, the solution
gets cold (i.e., the beaker feels very cold). Based on this information, what is the temperature dependence
of ΔG?
A. ΔG is negative at all temperatures.
B. ΔG is positive at all temperatures.
C. ΔG is positive at low temperature and negative at high temperature.
D. ΔG is negative at low temperature and positive at high temperature.
E. ΔG is 0; the system is at equilibrium at all temperatures.
----------------------------------------------------------------------------------------------------------8. Which one of the following species cannot be a Lewis base?
A. F−
B. H2O
C. OH−
D. NH3
E. NH4+
----------------------------------------------------------------------------------------------------------9. Consider the following titration curve. Which of the following statements is/are TRUE?
i.
The acid is a diprotic acid
ii.
The acid is a triprotic acid
iii.
Point E represents the third equivalence point
iv.
Point A represents the first half-equivalence point
A. i only
B. ii only
C. i and iv only
D. ii and iii only
E. ii, iii, and iv only
----------------------------------------------------------------------------------------------------------10. A chemist adds 300 mL of a 0.34 M solution of HCl to 500 mL of a 0.10 M solution of HClO4. What
is the pOH of the resulting solution at 25 °C?
A. 13.3
B. 11.4
C. 2.06
D. 7.21
E. The pOH cannot be determined from the information provided.
----------------------------------------------------------------------------------------------------------11. Given the following data for aqueous solutions at 25°C, which one of the answer choices is the
strongest acid?
Pyridine, C5H5N (Kb = 1.7 × 10−9)
Acetic acid, CH3COOH (Ka = 1.8 × 10−5)
Phenol, C6H5OH (Ka = 1.3 × 10−10)
Hydrogen cyanide, HCN (Ka = 4.9 × 10−10)
---------------------------------------------------A. HCN
B. C6H5O−
C. CH3COOH
D. C5H5NH+
E. C6H5OH
----------------------------------------------------------------------------------------------------------12. The concentration of ascorbic acid (vitamin C) in a solution is 0.0023 M. What is the pH of the
solution?
Structure of ascorbic acid
For ascorbic acid, Ka1 = 8.0 × 10–5, Ka2 = 1.6 × 10–12
A. 3.4
B. 4.1
C. 6.7
D. 7.2
E. 10.6
----------------------------------------------------------------------------------------------------------13. Oh no! A research student working in the lab of Rick T. Cat accidentally mixed up three un-labeled
bottles of 0.1 M acid solutions. He knows that the three acids are acetic acid, hypochlorous acid, and
nitric acid. In order to figure out the identities of the three solutions, Dr. Cat titrates each of them with
0.10 M NaOH. The following data were obtained at 25oC:
What are the identities of the acid solutions?
Ka (CH3COOH) = 1.8 × 10−5
Ka (HClO) = 3.5 × 10−8
Acid 1
Acid 2
Acid 3
A.
HClO
HNO3
CH3COOH
B.
HClO
CH3COOH
HNO3
C.
CH3COOH
HClO
HNO3
D.
CH3COOH
HNO3
HClO
E.
HNO3
HClO
CH3COOH
----------------------------------------------------------------------------------------------------------14. Benadryl is an over-the-counter drug that acts as an antihistamine. It is used to treat a number of
conditions that include allergies, insomnia, and motion sickness. What is the pH of a 0.0098 M solution
of a dose of the liquid form (an aqueous solution) of benadryl at 25oC?
Kb = 1.0 × 10−5
Structure of benadryl:
A. 3.50
B. 4.82
C. 7.00
D. 8.73
E. 10.50
----------------------------------------------------------------------------------------------------------15. Which one of the following salts will form an aqueous solution with the highest pH?
A. KIO
B. LiBrO
C. KClO
D. NaClO2
E. LiClO3
----------------------------------------------------------------------------------------------------------16. Which of the following statements are true concerning an aqueous solution of phosphoric acid
(H3PO4)? The acid dissociation constants of H3PO4 (aq) at 298 K are as follows:
Ka1 = 7.5 × 10−3, Ka2 = 6.2 × 10−8 , Ka3 = 4.2 × 10−13
i.
ii.
iii.
The strongest conjugate base involved is the PO43– (aq) species.
Both HPO42– (aq) and H2PO4– (aq) species are amphoteric.
HPO42– (aq) is a stronger acid than H2PO4– (aq).
A. i only
B. ii only
C. iii only
D. i and ii only
E. ii and iii only
----------------------------------------------------------------------------------------------------------17. Sorbic acid (C5H7COOH) is a monoprotic weak acid with Ka = 1.7 × 10–5. Its salt (potassium sorbate)
is added to cheese to inhibit the formation of mold. What is the pH of a 0.0428 M C5H7COOK aqueous
solution at 25°C?
A. 12.35
B. 9.58
C. 8.70
D. 5.90
E. 3.46
----------------------------------------------------------------------------------------------------------18. The Kw for water at body temperature (36.9°C) is 2.51 × 10–14. What is the pOH of blood if the pH is
7.40?
A. 5.8
B. 6.2
C. 6.6
D. 7.8
E. 13.6
----------------------------------------------------------------------------------------------------------19. The drawing below represents a buffer composed of equal concentrations of a weak acid HA and its
conjugate base A−. The solution is 1 M in each component, and the total volume is 1 L.
Which drawing below illustrates the composition of the solution after 10 mL of 2 M HCl is added?
----------------------------------------------------------------------------------------------------------20. A scientist titrates 50 mL of a 0.5 M solution of methylamine (CH3NH2) with 1 M HCl. What is the
pH of the solution after 12.5 mL of HCl is added at 25 oC?
Kb of methylamine = 4.2 × 10−4
A. 3.4
B. 5.9
C. 7.0
D. 10.6
E. 13.7
-----------------------------------------------------------------------------------------------------------
21. Given 1.00 L of a solution that is 0.100 M in sodium propionate (NaC3H5O2) and 0.300 M in
propionic acid (HC3H5O2), what is the pH after 0.0400 mole of HNO3 is added? (Assume that the volume
does not change upon addition of the HNO3.)
(Ka for HC3H5O2 = 1.3 × 10−5)
A. 4.50
B. 4.08
C. 3.96
D. 4.13
E. 4.62
----------------------------------------------------------------------------------------------------------22. In acidic solution, which statement is TRUE?
A. [H3O+] = [OH–]
B. [H3O+] = 0
C. [H3O+] > [OH–]
D. [H3O+] < [OH–]
E. [OH–] = 0
--------------------------------------------------------------------------------------------------------------------23. The famous scientist, Rick T. Cat, found himself at the Mt. Nittany Medical Center with symptoms
including hyperventilation, vomiting, dizziness, and a diffuse burning sensation. Upon examination, it
was found that his blood concentration of H2CO3 was 1.5 mmol/L, and the concentration of HCO3− in his
blood was 30 mmol/L. What was the pH of his blood?
Ka1 of H2CO3 = 4.3 × 10−7
Ka2 of H2CO3 = 5.6 × 10−11
A. 7.33
B. 11.55
C. 6.37
D. 7.67
E. 7.51
----------------------------------------------------------------------------------------------------------24. A scientist titrates 100 mL of a 0.2 M solution of hypobromous acid (HBrO) with 0.1 M NaOH.
What is the pH of the solution after 400 mL of NaOH is added at 25oC?
Ka (HBrO) = 2.5 × 10−9
A. 1.4
B. 3.8
C. 7.0
D. 12.6
E. 8.3
------------------------------------------------------------------------------------------------------------------25. After the glucose-phosphate species forms in the metabolic process, the isomerization of glucosephosphate to fructose-phosphate occurs. If the equilibrium constant for the isomerization reaction at
37°C (body temperature) is 0.65, what is the value of ΔG when the ratio of glucose-phosphate to
fructose-phosphate is 10 to 1?
glucose-phosphate → fructose-phosphate
Keq = 0.65
A. −0.48 kJ/mol
B. −0.63 kJ/mol
C. −1.11 kJ/mol
D. −4.82 kJ/mol
E. −6.93 kJ/mol
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------END OF EXAM
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Answer Key:
1. E
2. C
3. D
4. E
5. D
6. E
7. C
8. E
9. C
10. A
11. C
12. A
13. B
14. E
15. A
16. D
17. C
18. B
19. C
20. D
21. D
22. C
23. D
24. D
25. D