112 Sp12 Ex2-A - Chemistry Courses

Chemistry 112
Name
_______________________
Exam II Form A
Section
_______________________
February 29, 2012
eMail
_______________________
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.
CHEMISTRY 112 EXAM 2
February 29, 2012
FORM A
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What is the pH of a 0.2 M HCl solution?
A. 0.0
B. 2.0
C. 1.0
D. 0.7
E. 0.4
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The conjugate base of H2PO4– is:
A. H3PO4
B. HPO42−
C. PO43−
D. H3O+
E. OH−
There are 24 questions on this exam. Check that you have done all of the problems and filled in the
first 24 bubbles on the scantron. 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.
Your grade will be based only on what is on the scantron form.
The answer key will be posted on the web after the exam (on the Exam Schedule page).
You must turn in your cover sheet with your scantron answer form.
Hints
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As you read the question, underline or circle key words to highlight them for yourself.
Avoid errors from "mis-reading" the question.
Pay attention to units and magnitudes (decimal places) of numbers obtained from
calculations.
There is no penalty for guessing.
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A 0.1 M solution of a chemical substance has a pH of 4. The chemical substance is
A. a strong acid.
B. a strong base.
C. a weak acid.
D. a weak base.
E. not dissociated into ions in water.
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What is the percent dissociation of a 0.20 M solution of C3H7COOH (Ka = 1.5 x 10−5)?
A. 0.87%
B. 1.2 %
C. 12%
D. 55%
E. 99%
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2
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A 100 ml portion of water is added to each of the following two solutions.
1. 100 ml of 0.02 M KBr
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0.05 M solutions of several different acids are titrated with 0.1 M KOH. The acid for
which the pH at the equivalence point will be the highest is
2. 100 ml of 0.02 M KOH
A. HCl
Which of the following statements is correct?
A. There will be no change in pH of solutions 1 and 2.
B. The pH of solution 1 will remain the same but that of solution 2 will increase.
C. The pH of solution 1 will remain the same but that of solution 2 will decrease.
D. The pH of solution 2 will remain the same but that of solution 1 will increase.
E. The pH of solution 2 will remain the same but that of solution 1 will decrease.
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Which of the following is unlikely to act as a Lewis base?
B. HOCl (Ka = 3.0  10−8)
C. HF (Ka = 6.8 x 10−4)
D. HCN (Ka = 4.9  10−10)
E. HN3 (Ka = 1.9  10−5)
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What is the pH of 0.1 M Ca(NO2)2? (Ka for HNO2 = 4.5 x 10−4)
A. 12.2
B. 8.3
C. 7.5
D. 2.7
E. 9.3
A. CH4
B. NH3
C. H2O
D. O2–
E. F–
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Which of the following will give the solution with the highest pH when dissolved in
water?
A. NaCl
B. NaOCl
C. NaOClO
D. NaOClO2
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What is the concentration of S2− in a 0.40 M solution of H2S?
(Ka1 = 9.5 x 10−8; Ka2 =1.0 x 10−19)
A. 0.40 M
B. 0.20 M
C. 9.5 x 10−8 M
D. 1.0 x 10−19 M
E. NaOClO3
-----------------------------------------------------------------------------------------------------------------------8. For a given indicator HIn, the following equilibrium applies,
HIn = H+ + In−
Ka = 1.3 x 10−5
The indicator is red at pH < 4 and blue at pH > 6. Which of the following is false?
A. The indicator is a weak acid.
B. In 0.1 M NaOH, the indicator will appear blue.
C. In 0.2 M NaNO2, the indicator will be red (Ka for HNO2 = 4.5 x 10−4).
D. In 0.05 M HCl, the indicator will be red.
E. At pH = 11.5, the indicator will be mainly in the In− form.
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Go on to the next page E. 5.2 x 10−11 M
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Which of the following will give an acidic solution when dissolved in water?
1. FeCl3
2. NaCl
3. NH4Cl
4. NaF
(Ka for HF = 6.8 x 10−4)
A. 1 only
B. 2 and 4
C. 1 and 3
D. 3 only
E. 1, 2, and 3
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What is the value of the equilibrium constant for the following reaction?
(Ka for HF = 6.8 x 10−4).
F− (aq) + H2O(l)  HF(aq) + OH− (aq)
-----------------------------------------------------------------------------------------------------------------------Acetic acid dissociates according to the reaction CH3COOH(aq)  H+(aq) + CH3COO− (aq).
17.
At 25oC, the equilibrium constant Ka is 1.8 x 10−5.
For this reaction:
A. Ka decreases as the temperature increases
B. The reaction is exothermic
C. The entropy change is zero.
D. The standard free energy change is zero.
E. The standard enthalpy change is positive.
A. 4.5 x 10−4
B. 5.0 x 10−4
C. 2.0 x 10−4
D. 5.0 x 10−11
E. 1.5 x 10−11
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Which of the following solutions will result in a buffer?
A. 100 mL 0.20 M CH3COOH + 150 mL 0.25 M HCl
B. 100 mL 0.20 M KOH + 50 mL 0.20 M HCl
C. 100 mL 0.20 M CH3COONa + 50 mL 0.25 M NaOH
D. 100 mL 0.20 M CH3COONa + 50 mL 0.20 M HCl
E. 100 mL 0.20 M NH3 + 150 mL 0.25 M HCl
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If 25 mL of 0.231 M NH3 and 25 mL of 0.125 M HBr are combined, what is the pH of
the resulting solution?
Kb (NH3) = 1.8  10−5
A. 8.78
B. 9.34
C. 9.19
D. 4.80
E. 9.01
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Which reaction below should have S > 0 ?
A. 2 H2 (g) + O2 (g)  2 H2O (g)
B. 2 NO2 (g)  N2O4 (g)
C. H+ (aq) + F− (aq)  HF (aq)
D. BaF2 (s) + H2O (l)  Ba2+ (aq) + 2 F− (aq)
E. 2 Hg (l) + O2 (g)  2 HgO (s)
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Which of the following will have the highest gas-phase entropy at 25°C?
A. H2
B. C2H6
C. CH4
D. C3H8
E. C2H2
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Which of the following is NOT always true, according to the laws of thermodynamics?
A. Heat flow from a hot object to a colder one is a spontaneous process
B. The entropy of the universe increases in a spontaneous process
C. The free energy of the system decreases in a spontaneous process
D. The entropy of a pure element is zero.
E. For a process at equilibrium, the free energy change of the system is zero.
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Which of the following is always true for a spontaneous process, according to the second
law of thermodynamics?
A. The enthalpy of the system decreases
B. The entropy of the system increases
C. The free energy of the system increases
D. The free energy change of the system is zero
E. None of the above
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Consider the following reaction:
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Calculate the Go (in kJ) for the following reaction at 500K.
A+BC+D
Cu (s) + H2O (g)  CuO (g) + H2 (g)
The reaction will always be spontaneous when H is __ and S is __.
A. +, +
B. −, −
Cu (s)
H2O (g)
Hfo (kJ/mol)
0
–241.8
C. −, +
D. +, −
CuO (g)
H2 (g)
–155.2
0
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When Spring finally comes to State College, the temperature of the air rises into the 50's and
the snow begins to melt. Under these conditions, the values of H, S, and G for the
process (snow  water) are, respectively:
A. negative, positive, positive
B. positive, negative, negative
C. positive, positive, positive
D. positive, positive, negative
E. negative, positive, zero
So (J/K)
33.3
188.7
43.5
130.6
A. +110.6
B. –86.6
C. +23.9
D. –62.6
E. +301
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END OF EXAM
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Assuming that H and S do not vary with temperature, at what temperature will the
following reaction become spontaneous?
C (s) + H2O (g)  CO (g) + H2 (g); Ho = 131.3 kJ,
So = 133.6 J/K
A. 273°C
B. 325°C
C. 552°C
D. 710°C
E. The reaction will never become spontaneous
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