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Practice Test 3 Spring 2019
Practice Test for Exam 3
Dr Cabirac Lecture
1. For PbCl2 (Ksp = 2.4 x 10-4 ), will a precipitate of PbCl2 form when 0.10 L of 3.0 x 10-2 M Pb(NO3)2 is
added to 400 mL of 9.0 x 10-2 M NaCl?
A. Yes, because Q > Ksp.
B. No, because Q < Ksp
C. No, because Q = Ksp
D. Yes, because Q < Ksp.
2. The molar solubility of tin(II) iodide is 1.28 x 10-2 mol/L. What is Ksp for this compound?
A. 8.4 x 10-6
B. 1.28 x 10-2
C. 4.2 x 10-6
D. 1.6 x 10-4
E. 2.1 x 10-6
3. The Ksp for silver(I) phosphate is 1.8 x 10-18. Determine the silver ion concentration in a saturated
solution of silver(I) phosphate.
A. 1.6 x 10-5 M
B. 2.1 x 10-5 M
C. 3.7 x 10-5 M
D. 1.1 x 10-13 M
E. 4.8 x 10-5 M
4. Calculate the molar solubility of BaCO3 in a 0.10 M solution of Na2CO3 (aq).
(Ksp (BaCO3 ) = 8.1 x 10-9 )
A. 8.1 x 10-9 M
B. 9.0 x 10-5 M
C. 8.1 x 10-8 M
D. 2.8 x 10-4 M
E. 0.10 M
5. Which of the following compounds is more soluble in acidic solution than in pure neutral
water?
A. BaCO3
B. CuI
C. PbCl2
D. AgBr
E. NH4NO3
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Practice Test 3 Spring 2019
6. Arrange these compounds in order of increasing standard molar entropy at 25°C:
C3H8(g), C2H4(g), ZnS(s), and H2O(l).
A. ZnS(s) < H2O(l) < C3H8(g) < C2H4(g)
B. C2H4(g) < H2O(l) < C3H8(g) < NaCl(s)
C. ZnS(s) < C3H8(g) < C2H4(g) < H2O(l)
D. C3H8(g) < C2H4(g) < H2O(l) < ZnS(s)
E. ZnS(s) < H2O(l) < C2H4(g) < C3H8(g)
7. Without reference to a table, arrange these reactions according to increasing ∆S.
1) CH4(g) + H2O(g) → CO(g) + 3H2(g)
2) C(s) + O2(g) → CO2(g)
3) H2O2(l) → H2O(l) + 1/2O2(g)
A. 1 < 3 < 2
B. 2 < 3 < 1
C. 2 < 1 < 3
D. 3 < 2 < 1
E. 3 < 1 < 2
8. Which of the following is expected to have zero entropy?
I. N2(g) at 273 K
II. SiO2(s, amorphous) at 0 K
III. NaCl(s) perfectly ordered crystal at 25 K
IV. Na(s) perfectly ordered crystal at 0 K
A. I and IV
B. III and IV
C. I and II
D. I, II, and III
E. IV only
9. Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk
metal from further corrosion.
4Al(s) + 3O2(g) → 2Al2O3(s)
Calculate ∆G° for this reaction, given that ∆G°f of aluminum oxide is –1576.4 kJ/mol.
A. –3152.8 kJ/mol
B. –1576.4 kJ/mol
C. –788.2 kJ/mol
D. 1576.4 kJ/mol
E. 3152.8 kJ/mol
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Practice Test 3 Spring 2019
10. The element oxygen was prepared by Joseph Priestley in 1774 by heating mercury(II)
oxide:
HgO(s) → Hg(l) + 1/2O2(g), ∆H° = 90.84 kJ/mol.
Estimate the temperature at which this reaction will become spontaneous under
standard state conditions.
S°(Hg) = 76.02 J/K·mol
S°(O2) = 205.0 J/K·mol
S°(HgO) = 70.29 J/K·mol
A. 108 K
B. 430 K
C. 620 K
D. 775 K
E. 840 K
11. The normal melting point of sulfur is 113 °C. If a sample of solid sulfur is at 95 °C, predict
the signs of ∆H, ∆S, and ∆G for the melting process at this temperature.
A. ∆H> 0, ∆S> 0, ∆G< 0
B. ∆H> 0, ∆S> 0, ∆G> 0
C. ∆H> 0, ∆S< 0, ∆G< 0
D. ∆H< 0, ∆S> 0, ∆G> 0
E. ∆H< 0, ∆S< 0, ∆G> 0
12. Calculate Kp at 298 K for the reaction SO2(g) + NO2(g) ⇌ SO3(g) + NO(g).
A. 6.99 x 10–7
B. 5.71 x 10–8
C. 14.2
D. 475
E. 1.42 x 106
13. The equilibrium constant for the reaction AgBr(s) Ag+(aq) + Br– (aq) is the solubility
product constant, Ksp = 7.7 x 10–13 at 25°C. Calculate ∆G for the reaction when
[Ag+] = 1.0 x 10–2 M and [Br–] = 1.0 x 10–3 M. Is the reaction spontaneous or nonspontaneous at these
concentrations?
A. ∆G = 69.1 kJ/mol, nonspontaneous
B. ∆G = –69.1 kJ/mol, spontaneous
C. ∆G = 97.5 kJ/mol, spontaneous
D. ∆G = 40.6 kJ/mol, nonspontaneous
E. ∆G = –97.5 kJ/mol, nonspontaneous
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Practice Test 3 Spring 2019
14. Consider the following diagram showing the free energy, G, changes during a hypothethical reaction
A(g) + B(g) → C(g). On the left are pure reactants A and B each at 1 atm and ono the right is pure
product C at 1 atm. Which of the following statements is false?
A. The minimum of the graph corresponds to the equilibrium mixture of reactants and products for this
reaction
B. At equilibrium all of A and B have reacted to give pure C.
C. The entropy change for this reaction is negative.
D. The ΔG for the reaction corresponds to the difference between the top left of the curve and the
bottom of the curve.
15. Kw for the auto-ionization of water, H2O(l) ⇌H+(aq) + OH– (aq), is 1.0 x 10–14. What are
the signs (+/–) of ∆S° and ∆H° for the reaction at 25°C?
A. ∆S° = (+) and ∆H° = (+)
B. ∆S° = (+) and ∆H° = (–)
C. ∆S° = (–) and ∆H° = (+)
D. ∆S° = (–) and ∆H° = (–)
16. Predict the normal boiling point of triethylborane (C6H15B) using the following data:
A. 92°C
B. –21°C
C. 21°C
D. 365°C
E. 256°C
17. For which one of the following acids is chlorine in the +5 oxidation state?
A. HCl
B. HClO
C. HClO2
D. HClO3
E. HClO4
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Practice Test 3 Spring 2019
18. What is the total number of moles (n) of electrons exchanged between the oxidizing agent and the
reducing agent in the overall redox equation:
Cr2O72-(aq) + 6Fe2+(aq) + 14H+(aq) → 2Cr3+(aq) + 6Fe3+(aq) + 7H2O(l)
A. 1
B. 2
C. 3
D. 6
E. 12
19. Complete and balance the following redox equation. What is the coefficient of OH– when the equation is
balanced using the set of smallest whole-number coefficients?
MnO4– + I– → MnO2 + IO3– (basic solution)
A. 1
B. 2
C. 4
D. 10
E. None of these.
20. Given the following notation for an electrochemical cell, what is the balanced overall cell reaction?
Pt(s) | H2(g) | H+(aq) || Ag+(aq) | Ag(s)
A. 2H+(aq) + 2Ag+(aq) → H2(g) + 2Ag(s)
B. H2(g) + 2Ag(s) → H+(aq) + 2Ag+(aq)
C. 2H+(aq) + 2Ag(s) → H2(g) + 2Ag+(aq)
D. H2(g) + Ag+(aq) → H+(aq) + Ag(s)
E. H2(g) + 2Ag+(aq) → 2H+(aq) + 2Ag(s)
21. Consider an electrochemical cell constructed from the following half cells, linked by a KCl salt bridge.
- a Fe electrode in 1.0 M FeCl2 solution
- a Sn electrode in 1.0 M Sn(NO3)2 solution
When the cell is running spontaneously, which choice includes only true statements and no false ones?
A. The tin electrode loses mass and the tin electrode is the cathode.
B. The tin electrode gains mass and the tin electrode is the cathode.
C. The iron electrode gains mass and the iron electrode is the anode.
D. The iron electrode loses mass and the iron electrode is the cathode.
E. The iron electrode gains mass and the iron electrode is the cathode.
22. Calculate E°cell for a silver-aluminum cell in which the cell reaction is
Al(s) + 3Ag+(aq) → Al3+(aq) + 3Ag(s).
A. –2.46 V
B. 0.86 V
C. –0.86 V
D. 2.46 V
E. none of these
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Practice Test 3 Spring 2019
23. Consider an electrochemical cell based on the following cell diagram:
Pt | Pu3+(aq), Pu4+(aq) || Cl2(g), Cl– (aq) | Pt
Given that the standard cell emf is 0.35 V and that the standard reduction potential of chlorine is 1.36 V,
what is the standard reduction potential E°(Pu4+/Pu3+)?
A. 2.37 V
B. 1.01 V
C. –1.71 V
D. –1.01 V
E. 1.71 V
24. The half-cell reaction for the oxidation of H2O(l) to O2(g) is given below.
2H2O(l) → O2(g) + 4H+(aq) + 4e–
Which choice lists all of the following species that can oxidize H2O to O2(g) under standard-state
conditions?
MnO4–(aq), Cl2(g), Pb2+(aq), Cl– (aq), Ag+(aq)
A. Cl–(aq) only
B. Cl2(g) only
C. Pb2+(aq) and Ag+(aq)
D. Cl–(aq) and MnO4–(aq)
E. MnO4–(aq) and Cl2(g)
25. Consider the following standard reduction potentials in acid solution:
The strongest reducing agent among those shown above is
A. Fe3+.
B. Fe2+.
C. Br–.
D. Al3+.
E. Al.
26. Consider the following reaction: 2Fe2+(aq) + Cu2+ → 2Fe3+(aq) + Cu.
When the reaction comes to equilibrium, what is the cell voltage?
A. 0.43 V
B. 1.11 V
C. 0.78 V
D. –0.43 V
E. 0 V
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Practice Test 3 Spring 2019
27. Calculate ∆G° for the electrochemical cell Pb(s) | Pb2+(aq) || Fe3+(aq) | Fe2+(aq) | Pt(s).
A. –1.2 x 102 kJ/mol
B. –1.7 x 102 kJ/mol
C. 1.7 x 102 kJ/mol
D. –8.7 x 101 kJ/mol
E. –3.2 x 105 kJ/mol
28. For the electrochemical cell Ni(s) | Ni2+(1 M) || H+(1 M) | H2(1 atm) | Pt(s), which one of
the following changes will cause a decrease in the cell voltage?
A. Increase the pressure of H2 to 2.0 atm.
B. Decrease the mass of the nickel electrode.
C. Lower the pH of the cell electrolyte.
D. Decrease the concentration of Ni2+ ion.
E. None of the above.
29. The measured voltage of the cell Pt(s) | H2 (1.0 atm) | H+(aq) || Ag+(1.0 M) | Ag(s) is
1.02 V at 25°C. Calculate the pH of the solution.
A. 1.86
B. 1.69
C. 3.72
D. 3.89
E. 7.43
30. Which one of the following reactions must be carried out in an electrolytic cell rather than
in a galvanic cell?
A. Zn2+(aq) + Ca(s) → Zn(s) + Ca2+(aq)
B. Al3+(aq) + 3Br–(aq) → Al(s) + (3/2)Br2(l)
C. 2Al(s) + 3Fe2+(aq) → 2Al3+(aq) + 3Fe(s)
D. H2(g) + I2(s) → 2H+(aq) + 2I–(aq)
E. Fe2+(aq) + Mg(s) → Fe(s) + Mg2+(aq)
31. Which one of the following is consistent with a galvanic cell?
A. ∆G < 0, Ecell > 0, Q < K
B. ∆G < 0, Ecell < 0, Q < K
C. ∆G < 0, Ecell < 0, Q > K
D. ∆G > 0, Ecell < 0, Q < K
E. ∆G > 0, Ecell < 0, Q > K
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Practice Test 3 Spring 2019
32. Iron objects such as storage tanks and underground pipelines can be protected from
corrosion by connecting them through a wire to a piece of
A. Pb.
B. Ag.
C. Sn.
D. Mg
E. Cu
33. A metal object is to be gold-plated by an electrolytic procedure using aqueous AuCl3
electrolyte. Calculate the number of moles of gold deposited in 3.0 min by a constant
current of 10. A.
A. 6.2 x 10–3 mol
B. 9.3 x 10–3 mol
C. 1.8 x 10–2 mol
D. 3.5 x 10–5 mol
E. 160 mol
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Practice Test 3 Spring 2019
R = 8.314 J/molK F = 96,500 J/Vmol charge(C) = amp(C/s) x time (s)
1mol e- = 96,500 coulomb (C)
𝛥𝐺° = −𝑅𝑇𝑙𝑛𝐾 𝛥𝐺 = 𝛥𝐺° + 𝑅𝑇𝑙𝑛𝑄
E°cell = E°red(cathode) = E°red(anode) 𝛥𝐺 = −𝑛𝐹𝐸𝑐𝑒𝑙𝑙 𝛥𝐺° = −𝑛𝐹𝐸°𝑐𝑒𝑙𝑙
𝐸°𝑐𝑒𝑙𝑙 =0.0257
𝑛𝑙𝑛𝐾 𝐸𝑐𝑒𝑙𝑙 = 𝐸°𝑐𝑒𝑙𝑙 −0.0257
𝑛𝑙𝑛𝑄
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