Question 1

Which of the following statements about voltaic and electrolytic cells is correct?

Accepted Answer

A)  The anode will definitely gain weight in a voltaic cell. 
B)  Oxidation occurs at the cathode of both cells. 
C)  The free energy change, ΔG, is negative for the voltaic cell. 
D)  The electrons in the external wire flow from cathode to anode in an electrolytic cell. 
E)  None of these choices are correct. 
A)  The anode will definitely gain weight in a voltaic cell. 
B)  Oxidation occurs at the cathode of both cells. 
C)  The free energy change, ΔG, is negative for the voltaic cell. 
D)  The electrons in the external wire flow from cathode to anode in an electrolytic cell. 
E)  None of these choices are correct.

Question 2

A concentration cell consists of two Zn/Zn2+ electrodes. The electrolyte in compartment A is 0.10 M Zn(NO3)2 and in compartment B is 0.60 M Zn(NO3)2. What is the voltage of the cell at 25°C?

Accepted Answer

A)  0.010 V 
B)  0.020 V 
C)  0.023 V 
D)  0.046 V 
E)  None of these choices are correct. 
A)  0.010 V 
B)  0.020 V 
C)  0.023 V 
D)  0.046 V 
E)  None of these choices are correct.

Question 3

When the following redox equation is balanced with smallest whole number coefficients, the coefficient for zinc will be Zn(s) + ReO4(aq) → Re(s) + Zn2+(aq) (acidic solution)

Accepted Answer

A)  2. 
B)  7. 
C)  8. 
D)  16. 
E)  None of these choices are correct. 
A)  2. 
B)  7. 
C)  8. 
D)  16. 
E)  None of these choices are correct.

Question 4

Calculate E° cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. O2(g) + 4H+(aq) + 4e-
    2H2O(l) E° = 1.229 V
Al3+(aq) + 3e-
    Al(s) E° = -1.662 V
Overall reaction:
4Al(s) + 3O2(g) + 12H+(aq) → 4Al3+(aq) + 6H2O(l)

Accepted Answer

A)  E° cell = -2.891 V, nonspontaneous 
B)  E° cell = -2.891 V, spontaneous 
C)  E° cell = 2.891 V, nonspontaneous 
D)  E° cell = 2.891 V, spontaneous 
E)  None of these choices are correct. 
A)  E° cell = -2.891 V, nonspontaneous 
B)  E° cell = -2.891 V, spontaneous 
C)  E° cell = 2.891 V, nonspontaneous 
D)  E° cell = 2.891 V, spontaneous 
E)  None of these choices are correct.

Question 5

How many grams of oxygen gas will be produced in the electrolysis of water, for every gram of hydrogen gas formed? Reaction: 2H2O(l) → 2H2(g) + O2(g)

Accepted Answer

A)  31.7 g 
B)  15.9 g 
C)  7.94 g 
D)  3.97 g 
E)  1.98 g 
A)  31.7 g 
B)  15.9 g 
C)  7.94 g 
D)  3.97 g 
E)  1.98 g

Question 6

The lead-acid battery is an example of a secondary battery.

Accepted Answer

A) True 
 B)False

Question 7

Electrons are produced at the cathode of a voltaic cell.

Accepted Answer

A) True 
 B)False

Question 8

A secondary cell (battery) can operate either as a galvanic or an electrolytic cell.

Accepted Answer

A) True 
 B)False

Question 9

What product forms at the anode during the electrolysis of molten NaBr?

Accepted Answer

A)  Na+(l) 
B)  Na(l) 
C)  Br-(l) 
D)  Br3-(l) 
E)  Br2(g) 
A)  Na+(l) 
B)  Na(l) 
C)  Br-(l) 
D)  Br3-(l) 
E)  Br2(g)

Question 10

Calculate E° cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. H2O2(aq) + 2H+(aq) + 2e- 2H2O(l) E° = 1.77 V
Fe3+ (aq) + e- Fe2+(aq) E° = 0.77 V
Overall reaction:
2Fe3+(aq) + 2H2O(l) → H2O2(aq) + 2H+(aq) + 2Fe2+(aq)

Accepted Answer

A)  E° cell = -1.00 V, nonspontaneous 
B)  E° cell = -1.00 V, spontaneous 
C)  E° cell = 1.00 V, nonspontaneous 
D)  E° cell = 1.00 V, spontaneous 
E)  E° cell = -0.23 V, nonspontaneous 
A)  E° cell = -1.00 V, nonspontaneous 
B)  E° cell = -1.00 V, spontaneous 
C)  E° cell = 1.00 V, nonspontaneous 
D)  E° cell = 1.00 V, spontaneous 
E)  E° cell = -0.23 V, nonspontaneous

Question 11

Which of the following solids is commonly used as an inactive electrode in electrochemical cells?

Accepted Answer

A)  zinc 
B)  graphite 
C)  copper 
D)  iron 
E)  sodium 
A)  zinc 
B)  graphite 
C)  copper 
D)  iron 
E)  sodium

Question 12

The value of E° cell for the reaction 2Cr3+(aq) + 6Hg(l) → 2Cr(s) + 3Hg22+(aq)
Is 1.59 V. Calculate ΔG° for the reaction.

Accepted Answer

A)  -921 kJ 
B)  -767 kJ 
C)  -460 kJ 
D)  -307 kJ 
E)  None of these choices are correct. 
A)  -921 kJ 
B)  -767 kJ 
C)  -460 kJ 
D)  -307 kJ 
E)  None of these choices are correct.

Question 13

Examine the following half-reactions and select the weakest reducing agent among the substances. Cr(OH)3(s) + 3e-
    Cr(s) + 3OH-(aq) E° = -1.48 V
SnO2(s) + 2H2O(l) + 4e-
    Sn(s) + 4OH-(aq) E° = -0.945 V
MnO2(s) + 4H+(aq) + 2e-
    Mn2+(aq) + 2H2O(l) E° = 1.224 V
Hg2SO4(s) + 2e-
    2Hg(l) + SO42-(aq) E° = 0.613 V

Accepted Answer

A)  Cr(s) 
B)  Sn(s) 
C)  Mn2+(aq) 
D)  Hg(l) 
E)  OH-(aq) 
A)  Cr(s) 
B)  Sn(s) 
C)  Mn2+(aq) 
D)  Hg(l) 
E)  OH-(aq)

Question 14

A voltaic cell consists of a Ag/Ag+ electrode (E° = 0.80 V) and a Fe2+/Fe3+ electrode (E° = 0.77 V) with the following initial molar concentrations: [Fe2+] = 0.30 M; [Fe3+] = 0.10 M; [Ag+] = 0.30 M. What is the equilibrium concentration of Fe3+? (Assume the anode and cathode solutions are of equal volume, and a temperature of 25°C.)

Accepted Answer

A)  0.030 M 
B)  0.043 M 
C)  0.085 M 
D)  0.11 M 
E)  0.17 M 
A)  0.030 M 
B)  0.043 M 
C)  0.085 M 
D)  0.11 M 
E)  0.17 M

Question 15

A voltaic cell prepared using aluminum and nickel has the following cell notation. Al(s) | Al3+(aq) || Ni2+(aq) | Ni(s)
Which of the following reactions occurs at the anode?

Accepted Answer

A)  Al(s) → Al3+(aq) + 3e- 
B)  Al3+(aq) + 3e → Al(s) 
C)  Ni(s) → Ni2+(aq) + 2e- 
D)  Ni2+(aq) + 2e- → Ni(s) 
E)  None of these choices are correct. 
A)  Al(s) → Al3+(aq) + 3e- 
B)  Al3+(aq) + 3e → Al(s) 
C)  Ni(s) → Ni2+(aq) + 2e- 
D)  Ni2+(aq) + 2e- → Ni(s) 
E)  None of these choices are correct.

Question 16

A voltaic cell consists of a Cd/Cd2+ electrode (E° = -0.40 V) and a Fe/Fe2+ electrode (E° = -0.44 V). If Ecell = 0 and the temperature is 25°C, what is the ratio [Fe2+]/[Cd2+]?

Accepted Answer

A)  2 × 101 
B)  1 × 101 
C)  1 
D)  1 × 10-1 
E)  5 × 10-2 
A)  2 × 101 
B)  1 × 101 
C)  1 
D)  1 × 10-1 
E)  5 × 10-2

Question 17

Consider the reaction in the lead-acid cell Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(aq) + 2H2O(l)
For which E° cell = 2.04 V at 298 K. ΔG° for this reaction is

Accepted Answer

A)  -3.94 × 105 kJ. 
B)  -3.94 × 102 kJ. 
C)  -1.97 × 105 kJ. 
D)  -7.87 × 102 kJ. 
E)  None of these choices are correct. 
A)  -3.94 × 105 kJ. 
B)  -3.94 × 102 kJ. 
C)  -1.97 × 105 kJ. 
D)  -7.87 × 102 kJ. 
E)  None of these choices are correct.

Question 18

Which one of the following is not a redox reaction?

Accepted Answer

A)  Al(OH)4(aq) + 4H(aq) → Al3+(aq) + 4H2O(l) 
B)  C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) 
C)  Na6FeCl8(s) + 2Na(l) → 8NaCl(s) + Fe(s) 
D)  2H2O2(aq) → 2H2O(l) + O2(g) 
E)  CO2(g) + H2(g) → CO(g) + H2O(g) 
A)  Al(OH)4(aq) + 4H(aq) → Al3+(aq) + 4H2O(l) 
B)  C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) 
C)  Na6FeCl8(s) + 2Na(l) → 8NaCl(s) + Fe(s) 
D)  2H2O2(aq) → 2H2O(l) + O2(g) 
E)  CO2(g) + H2(g) → CO(g) + H2O(g)

Question 19

The following half-reactions occur in the mercury battery used in calculators. If E° cell = 1.357 V, calculate the equilibrium constant for the cell reaction at 25°C. (Assume the stoichiometric coefficients in the cell reaction are all equal to 1.) HgO(s) + H2O(l) + 2e-
    Hg(l) + 2OH-(aq)
ZnO(s) + H2O(l) + 2e-
    Zn(s) + 2OH-(aq)

Accepted Answer

A)  9.4 × 1022 
B)  7.5 × 1045 
C)  6.4 × 1063 
D)  7.8 × 1091 
E)  > 9.9 × 1099 
A)  9.4 × 1022 
B)  7.5 × 1045 
C)  6.4 × 1063 
D)  7.8 × 1091 
E)  > 9.9 × 1099

Question 20

Which component of the following cell notation is the anode? P |   || R | S

Accepted Answer

A)  P 
B)    
C)  R 
D)  S 
E)  One of the | symbols is the anode. 
A)  P 
B)    
C)  R 
D)  S 
E)  One of the | symbols is the anode.

Exam 21: Electrochemistry Chemical Change and Electrical Work

Which of the following statements about voltaic and electrolytic cells is correct?

A concentration cell consists of two Zn/Zn2+ electrodes. The electrolyte in compartment A is 0.10 M Zn(NO3)2 and in compartment B is 0.60 M Zn(NO3)2. What is the voltage of the cell at 25°C?

When the following redox equation is balanced with smallest whole number coefficients, the coefficient for zinc will be Zn(s) + ReO4(aq) → Re(s) + Zn2+(aq) (acidic solution)

Calculate E° cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. O2(g) + 4H+(aq) + 4e- 2H2O(l) E° = 1.229 V Al3+(aq) + 3e- Al(s) E° = -1.662 V Overall reaction: 4Al(s) + 3O2(g) + 12H+(aq) → 4Al3+(aq) + 6H2O(l)

How many grams of oxygen gas will be produced in the electrolysis of water, for every gram of hydrogen gas formed? Reaction: 2H2O(l) → 2H2(g) + O2(g)

The lead-acid battery is an example of a secondary battery.

Electrons are produced at the cathode of a voltaic cell.

A secondary cell (battery) can operate either as a galvanic or an electrolytic cell.

What product forms at the anode during the electrolysis of molten NaBr?

Calculate E° cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. H2O2(aq) + 2H+(aq) + 2e- 2H2O(l) E° = 1.77 V Fe3+ (aq) + e- Fe2+(aq) E° = 0.77 V Overall reaction: 2Fe3+(aq) + 2H2O(l) → H2O2(aq) + 2H+(aq) + 2Fe2+(aq)

Which of the following solids is commonly used as an inactive electrode in electrochemical cells?

The value of E° cell for the reaction 2Cr3+(aq) + 6Hg(l) → 2Cr(s) + 3Hg22+(aq) Is 1.59 V. Calculate ΔG° for the reaction.

A voltaic cell prepared using aluminum and nickel has the following cell notation. Al(s) | Al3+(aq) || Ni2+(aq) | Ni(s) Which of the following reactions occurs at the anode?

A voltaic cell consists of a Cd/Cd2+ electrode (E° = -0.40 V) and a Fe/Fe2+ electrode (E° = -0.44 V). If Ecell = 0 and the temperature is 25°C, what is the ratio [Fe2+]/[Cd2+]?

Consider the reaction in the lead-acid cell Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(aq) + 2H2O(l) For which E° cell = 2.04 V at 298 K. ΔG° for this reaction is

Which one of the following is not a redox reaction?

Which component of the following cell notation is the anode? P | || R | S

Keys to Studying Chemistry Definitions, Units, and Problem Solving

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces Liquids, Solids, and Phase Changes

The Properties of Mixtures Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Kinetics Rates and Mechanisms of Chemical Reactions

Equilibrium the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics Entropy, Free Energy, and Reaction Direction

The Elements in Nature and Industry

Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

A concentration cell consists of two Zn/Zn²⁺ electrodes. The electrolyte in compartment A is 0.10 M Zn(NO₃)₂ and in compartment B is 0.60 M Zn(NO₃)₂. What is the voltage of the cell at 25°C?

When the following redox equation is balanced with smallest whole number coefficients, the coefficient for zinc will be Zn(s) + ReO₄(aq) → Re(s) + Zn₂₊(aq) (acidic solution)

Calculate E°_cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. O₂(g) + 4H⁺(aq) + 4e^- 2H₂O(l) E° = 1.229 V Al³⁺(aq) + 3e^- Al(s) E° = -1.662 V Overall reaction: 4Al(s) + 3O₂(g) + 12H⁺(aq) → 4Al³⁺(aq) + 6H₂O(l)

How many grams of oxygen gas will be produced in the electrolysis of water, for every gram of hydrogen gas formed? Reaction: 2H₂O(l) → 2H₂(g) + O₂(g)

Calculate E°_cell and indicate whether the overall reaction shown is spontaneous or nonspontaneous. H₂O₂(aq) + 2H⁺(aq) + 2e^- 2H₂O(l) E° = 1.77 V Fe³⁺ (aq) + e^- Fe²⁺(aq) E° = 0.77 V Overall reaction: 2Fe³⁺(aq) + 2H₂O(l) → H₂O₂(aq) + 2H⁺(aq) + 2Fe²⁺(aq)

The value of E°_cell for the reaction 2Cr³⁺(aq) + 6Hg(l) → 2Cr(s) + 3Hg₂²⁺(aq) Is 1.59 V. Calculate ΔG° for the reaction.

A voltaic cell prepared using aluminum and nickel has the following cell notation. Al(s) | Al₃₊(aq) || Ni₂₊(aq) | Ni(s) Which of the following reactions occurs at the anode?

A voltaic cell consists of a Cd/Cd²⁺ electrode (E° = -0.40 V) and a Fe/Fe²⁺ electrode (E° = -0.44 V). If E_cell = 0 and the temperature is 25°C, what is the ratio [Fe²⁺]/[Cd²⁺]?

Consider the reaction in the lead-acid cell Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(aq) + 2H₂O(l) For which E°_cell = 2.04 V at 298 K. ΔG° for this reaction is