Chapter 20 Review Questions PDF

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Chapter 20 Review Questions...

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Chapter 20 Review Questions

1R) Which element is reduced in the reaction below? Fe(CO)5 (l) + 2HI (g) → Fe(CO)4I2 (s) + CO (g) + H2 (g) A) Fe C) O E) I

B) C D) H Answer: D

2R) Which element is reduced in the reaction below? Fe2+ + H+ + Cr2O72- → Fe3+ + Cr3+ + H2O A) Fe C) O

B) Cr D) H

Answer: B

4R) Which of the following reactions is a redox reaction? (a) K2CrO4 + BaCl 2 → BaCrO4 + 2KCl (b) Pb22+ + 2Br- → PbBr (c) Cu + S → CuS A) (a) only C) (c) only E) (b) and (c)

B) (b) only D) (a) and (c) Answer: C

6R) Which substance is the oxidizing agent in the following reaction? Fe2S3 + 12HNO3 → 2Fe(NO3)3 + 3S + 6NO2 + 6H2O A) HNO3

B) S

C) NO2

D) Fe2S3

E) H2O

Answer: A

7R) What is the coefficient of the permanganate ion when the following equation is balanced? MnO4- + Br- → Mn2+ + Br2 A) 1 C) 3 E) 4

(acidic solution)

B) 2 D) 5 Answer: B

8R) What is the coefficient of the dichromate ion when the following equation is balanced? Fe2+ + Cr2O72- → Fe3+ + Cr3+ A) 1 B) 2 C) 3 D) 5 E) 6

(acidic solution)

Answer: A

10R) Which transformation could take place at the anode of an electrochemical cell? A) Cr2O72- → Cr2+ B) F2 to FC) O2 to H2O D) HAsO2 to As E) None of the above could take place at the anode.

Answer: E

11R) The purpose of the salt bridge in an electrochemical cell is to ________. A) maintain electrical neutrality in the half-cells via migration of ions B) provide a source of ions to react at the anode and cathode C) provide oxygen to facilitate oxidation at the anode D) provide a means for electrons to travel from the anode to the cathode E) provide a means for electrons to travel from the cathode to the anode

Answer: A

13R) Which transformation could take place at the cathode of an electrochemical cell? A) MnO2 → MnO4B) Br2 → BrO3C) NO → HNO2 D) HSO4- → H2SO3 E) Mn2+ → MnO4-

Table 20.1 Half Reaction F2 (g) + 2e- → 2F- (aq) Cl2 (g) + 2e- → 2Cl- (aq) Br2 (l) + 2e- → 2Br- (aq) O2 (g) + 4H+ (aq) + 4e- → 2H2O (l) Fe3+ (aq) + e- → Fe2+ (aq) I2 (s) + 2e- → 2I- (aq) Cu2+ + 2e- → Cu (s) 2H+ + 2e- → H2 (g) Pb2+ + 2e- → Pb (s) Ni2+ + 2e- → Ni (s) Li+ + e- → Li (s)

Answer: D

E°(V) +2.87 +1.359 +1.065 +1.23 +0.771 +0.536 +0.34 0 -0.126 -0.28 -3.05

14R) Which of the halogens in Table 20.1 is the strongest oxidizing agent? A) Cl2 B) Br2 C) F2 D) I2 E) All of the halogens have equal strength as oxidizing agents.

Answer: C

15R) Which one of the following types of elements is most likely to be a good oxidizing agent? A) alkali metals B) lanthanides C) alkaline earth elements D) transition elements E) halogens

Answer: E

Table 20.2

17R) Which of the following reactions will occur spontaneously as written? A) Sn4+ (aq) + Fe3+ (aq) → Sn2+ (aq) + Fe2+ (aq) B) 3Fe (s) + 2Cr3+ (aq) → 2Cr (s) + 3Fe2+ (aq) C) Sn4+ (aq) + Fe2+ (aq) → Sn2+ (aq) + Fe (s) D) 3Sn4+ (aq) + 2Cr (s) → 2Cr3+ (aq) + 3Sn2+ (aq) E) 3Fe2+ (aq) → Fe (s) + 2Fe3+ (aq)

Answer: D

21R) What is the anode in an alkaline battery? B) KOH

A) MnO2 C) Zn powder

D) Mn2O3

E) Pt

Answer: C

22R) What is the cathode in an alkaline battery? A) MnO2

B) KOH

C) Zn powder

D) Mn2O3

E) Pt

Answer: A

23R) What is the cathode in the hydrogen fuel cell? A) O2

B) KOH

C) Li

D) H2

E) Pt

Answer: A

11R) What is the oxidation number of potassium in KMnO4? A) 0 C) +2 E) +3

B) +1 D) -1 Answer: B

12R) What is the oxidation number of manganese in the MnO41- ion? A) +1 C) +5 E) +7

B) +2 D) +4 Answer: E

21R) The half-reaction occurring at the anode in the balanced reaction shown below is ________. 3MnO4- (aq) + 24H+ (aq) + 5Fe (s) → 3Mn2+ (aq) + 5Fe3+ (aq) + 12H2O (l) A) MnO4- (aq) + 8H+ (aq) + 5e- → Mn2+ (aq) + 4H2O (l) B) 2MnO4- (aq) + 12H+ (aq) + 6e- → 2Mn2+ (aq) + 3H2O (l) C) Fe (s) → Fe3+ (aq) + 3eD) Fe (s) → Fe2+ (aq) + 2eE) Fe2+ (aq) → Fe3+ (aq) + e-

Answer: C

25R) 1V = ________. B) 1 J/s D) 1 J/C

A) 1 amp ∙ s C) 96485 C E) 1 C/J

Answer: D

26R) The more ________ the value of E°red, the greater the driving force for reduction. A) positive C) exothermic E) extensive

B) negative D) endothermic Answer: A

Table 20.2

27R) The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. Sn2+ (aq) + 2Fe3+ (aq) → 2Fe2+ (aq) + Sn4+ (aq) A) +0.46 C) +1.39 E) +1.21

B) +0.617 D) -0.46 Answer: B

30R) The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. 3Sn4+ (aq) + 2Cr (s) → 2Cr3+ (aq) + 3Sn2+ (aq) A) +1.94 C) +2.53 E) -1.02

B) +0.89 D) -0.59 Answer: B

31R) The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by: A) ΔG =

B) ΔG =

C) ΔG = -nFE

D) ΔG = -nRTF

E) ΔG =

Answer: C

32R) The standard cell potential (E°cell) of the reaction below is +0.126 V. The value of ΔG° for the reaction is ________ kJ/mol. Pb (s) + 2H+(aq) → Pb2+ (aq) + H2 (g) A) -24.3 C) -12.6

B) +24.3 D) +12.6

E) -50.8

Answer: A

34R) The standard cell potential (E°cell) of the reaction below is -0.34 V. The value of ΔG° for the reaction is ________ kJ/mol. Cu (s) + 2H+ (aq) → Cu2+ (aq) + H2 (g) A) -0.34 B) +66 C) -130 D) +130 E) none of the above

Answer: B

15R) The standard cell potential (E° cell) for the reaction below is +0.63 V. The cell potential for this reaction is ________ V when [ Zn2+] = 3.0 M and [Pb2+] = 2.0 × 10-4 M. Pb2+ (aq) + Zn (s) → Zn2+ (aq) + Pb (s) A) 0.51 C) 0.40 E) 0.63

B) 0.86 D) 0.75 Answer: A

16R) The standard cell potential (E° cell) for the reaction below is +1.10 V. The cell potential for this reaction is ________ V when the concentration of [Cu2+] = 1.0 × 10-5 M and [Zn2+] = 3.0 M. Zn (s) + Cu2+ (aq) → Cu (s) + Zn2+ (aq) A) 1.42 C) 0.94 E) 1.10

B) 1.26 D) 0.78 Answer: C

20R) How many kilowatt-hours of electricity are used to produce 4.50 kg of magnesium in the electrolysis of molten MgCl2 with an applied emf of 5.00 V? A) 0.0201 C) 12.4 E) 24.8

B) 0.0496 D) 49.6 Answer: D Diff: 4

21R) The most useful ore of aluminum is bauxite, in which Al is present as hydrated oxides, Al2O3 · H2O.

The

number of kilowatt-hours of electricity required to produce 3.00 kg of aluminum from electrolysis of compounds from bauxite is ________ when the applied emf is 4.50 V. A) 0.0249 B) 0.0402 C) 26.8 D) 13.4 E) 40.2 Answer: E Diff: 4

29R) How many seconds are required to produce 1.0 g of silver metal by the electrolysis of a AgNO3 solution using a current of 60 amps? A) 5.4 × 104 B) 3.2 × 103 C) 15 D) 3.7 × 10-5 E) 30

Answer: C

30R) How many grams of copper will be plated out by a current of 2.3 A applied for 35 minutes to a 0.50 M solution of copper (II) sulfate? A) 1.6 B) 3.2 C) 1.8 × 10-2 D) 3.6 × 10-2 E) 0.019

Answer: A

32R) How many minutes will it take to plate out 16.22 g of Al metal from a solution of Al 3+ using a current of 14.6 amps in an electrolytic cell? A) 53.0 B) 66.2 C) 153 D) 199 E) 11900

Answer: D

Extra 1) Balance the following reaction, which occurs in a basic solution.

Answer: 2MnO4- + Br- + H2O → BrO3 - + 2MnO2 + 2OH –

Extra 2) Balance the following reaction, which occurs in a basic solution. MnO4- + C2O4 2- → CO3 2- + MnO2

Answer: 2MnO4- + 3C2O4 2- + 4OH - → 6CO3 2- + 2MnO2 + 2H2O...