Chapter 19 Practice Test
1. Complete and balance the following redox equation. When properly balanced using the smallest whole-number coefficients, the coefficient of S is
H2S + HNO3 ® S + NO (acidic solution)
A. 1 B. 2 C. 3 D. 5 E. 6
2. Complete and balance the following redox equation. What is the coefficient of H2S when the equation is balanced using the set of smallest whole-number coefficients?
H2S + MnO4- ® Mn2+ + SO42- (acidic solution)
A. 1 B. 2 C. 4 D. 5 E. None of these.
3. 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.
4. Complete and balance the following redox equation using the set of smallest whole-number coefficients. Now sum the coefficients of all species in the balanced equation. (Remember the coefficients that are equal to one.) The sum of the coefficients is
BrO3-(aq) + Sb3+(aq) ® Br-(aq) + Sb5+(aq) (acidic solution)
A. 4 B. 12 C. 13 D. 17 E. None of these.
5. Given the following notation for an electrochemical cell
Pt(s) | H2(g) | H+(aq) || Ag+(aq) | Ag(s),
what is the balanced overall (net) cell reaction?
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)
6. 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.
7. A certain electrochemical cell has for its cell reaction:
Zn + HgO ® ZnO + Hg
Which is the half-reaction occurring at the anode?
A. HgO + 2e- ® Hg + O2-
B. Zn2+ + 2e- ® Zn
C. Zn ® Zn2+ + 2e-
D. ZnO + 2e- ® Zn
8. Calculate E°cell for the following reaction:
2Fe2+(aq) + Cd2+(aq) ® 2Fe3+(aq) + Cd(s)
A. -0.37 V B. 0.37 V C. -1.17 V D. 1.17 V E. None of these.
9. For the reaction Ni2+(aq) + 2Fe2+(aq) ® Ni(s) + 2Fe3+(aq), the standard cell potential E°cell is
A. +2.81 V. B. +1.02 V. C. +0.52 V. D. -1.02 V. E. -2.81 V.
10. Consider the following electrochemical cell:
U | U3+(aq) || Cl-(aq),Cl2(g) | Pt
If the standard cell emf is 3.16 V, what is the standard reduction potential for uranium?
A. -3.16 V B. +3.16 V C. -1.80 V D. +1.80 V E. +1.36 V
11. An electrochemical cell based on the following reaction has a standard cell voltage (E°cell) of 0.48 V:
Sn(s) + Cu2+(aq) ® Sn2+(aq) + Cu(s)
What is the standard reduction potential of tin(II)? (E°(Cu2+/Cu) = 0.34 V)
A. -0.14 V B. 0.14 V C. -0.82 V D. 0.82 V E. none of these
12. Which statement is true for a spontaneous redox reaction carried out at standard-state conditions?
A. E°red is always negative.
B. E°cell is always positive.
C. E°ox is always positive.
D. E°red is always positive.
13. Consider the following standard reduction potentials in acid solution:
E°(V)
Al3+(aq) + 3e- ® Al(s) -1.66
Sn4+(aq) + 2e- ® Sn2+(aq) +0.14
I2(s) + 2e- ® 2I- (aq) +0.53
Which is the weakest oxidizing agent in this list?
A. Al3+(aq) B. Al(s) C. I-(aq) D. I2(s) E. Sn4+(aq)
14. Consider the following standard reduction potentials in acid solution:
Cr3+ + 3e- ® Cr E° = -0.74 V
Co2+ + 2e- ® Co E° = -0.28 V
MnO4- + 8H+ + 5e- ® Mn2+ + 4H2O E° = +1.51 V
The strongest reducing agent listed above is
A. Cr3+. B. Cr. C. Mn2+. D. Co. E. MnO4-.
15. Using a table of standard reduction potentials, determine which of these reactions (if any) is/are nonspontaneous in the direction indicated at 25°C.
A. 2Fe3+ + 2Cl- ® 2Fe2+ + Cl2(g)
B. 2Fe3+ + 2Br- ® 2Fe2+ + Br2(l)
C. 2Fe3+ + 2I- ® 2Fe2+ + I2(s)
D. A and B
E. All are spontaneous.
16. Which one of the following reagents is capable of transforming Br- (aq) to Br2(l) under standard-state conditions?
A. I- (aq) B. NO3- (aq) C. Ag+(aq) D. Al3+(aq) E. Au3+(aq)
17. Determine the equilibrium constant (Keq) at 25°C for the reaction
Cl2(g) + 2Br- (aq) 2Cl- (aq) + Br2(l)
A. 1.5 ´ 10-10 B. 6.3 ´ 109 C. 1.3 ´ 1041 D. 8.1 ´ 104 E. 9.8
18. Calculate the cell emf for the following reaction at 25°C:
Ni(s) + 2Cu2+(0.010 M) ® Ni2+(0.0010 M) + 2Cu+(1.0 M)
A. 0.40 V B. -0.43 V C. 0.43 V D. 0.34 V E. 0.37 V
19. Calculate the cell voltage for the following reaction:
Cu2+ (0.010 M) + H2(1 atm) ® Cu(s) + 2H+( pH = 7.0)
A. 0.19 V B. -0.01 V C. 0.34 V D. 0.69 V E. 0.49 V
20. How many coulombs of charge are required to cause reduction of 0.20 mole of Cr3+ to Cr?
A. 0.60 C B. 3.0 C C. 2.9 ´ 104 C D. 5.8 ´ 104 C E. 9.65 ´ 104 C
21. 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 ´ 10-3 mol
B. 9.3 ´ 10-3 mol
C. 1.8 ´ 10-2 mol
D. 3.5 ´ 10-5 mol
E. 160 mol
22. How many grams of nickel would be electroplated by passing a constant current of 7.2 A through a solution of NiSO4 for 90.0 min?
A. 0.20 g B. 0.40 g C. 12 g D. 24 g E. 47 g