Question 1

Write a balanced half-reaction for the reduction of CrO42-(aq)to Cr(OH)3(s)in a basic solution.

Accepted Answer

A)  CrO42-(aq)+ 3 OH-(aq)+ 3 e- → Cr(OH)3(s)+ 2 O2(g) 
B)  CrO42-(aq)+ 3 H+(aq)+ 3 e- → Cr(OH)3(s) 
C)  CrO42-(aq)+ 3 H+(aq)→ Cr(OH)3(s)+ 2 e- 
D)  CrO42-(aq)+ 4 H2O(   )+ 3 e- → Cr(OH)3(s)+ 5 OH-(aq) 
E)  CrO42-(aq)+ 3 OH-(aq)→ Cr(OH)3(s)+ 2 O2(g) 
A)  CrO42-(aq)+ 3 OH-(aq)+ 3 e- → Cr(OH)3(s)+ 2 O2(g) 
B)  CrO42-(aq)+ 3 H+(aq)+ 3 e- → Cr(OH)3(s) 
C)  CrO42-(aq)+ 3 H+(aq)→ Cr(OH)3(s)+ 2 e- 
D)  CrO42-(aq)+ 4 H2O(   )+ 3 e- → Cr(OH)3(s)+ 5 OH-(aq) 
E)  CrO42-(aq)+ 3 OH-(aq)→ Cr(OH)3(s)+ 2 O2(g)

Question 2

Calculate the equilibrium constant for the following reaction at 25 °C, 2 IO3-(aq)+ 5 Hg(   )+ 12 H+(aq)→ I2(s)+ 5 Hg2+(aq)+ 6 H2O(   )
The standard reduction potentials are as follows:
IO3-(aq)+ 6 H+(aq)+ 5 e- → I2(s)+ 3 H2O(   )
E° = +1.20 V
Hg2+(aq)+ 2 e- → Hg(   )
E° = +0.86 V

Accepted Answer

A)  3 × 10-58 
B)  6 × 105 
C)  3 × 1011 
D)  6 × 1028 
E)  3 × 1057 
A)  3 × 10-58 
B)  6 × 105 
C)  3 × 1011 
D)  6 × 1028 
E)  3 × 1057

Question 3

Calculate the standard cell potential (   )for the reaction 2 Ag(s)+ Co2+(aq)→ 2 Ag+(aq)+ Co(s). The standard reduction potentials are as follows:
Ag+(aq)+ e−→ Ag(s)
E° = 0.8 V
Co2+(aq)+2 e−→ Co(s)
E° = -0.277 V

Accepted Answer

A)  -1.077 V 
B)  1.077 V 
C)  -1.877 V 
D)  1.877 V 
E)  1.323 V 
A)  -1.077 V 
B)  1.077 V 
C)  -1.877 V 
D)  1.877 V 
E)  1.323 V

Question 4

Primary batteries are also called storage batteries or rechargeable batteries.

Accepted Answer

A) True 
 B)False

Question 5

For the following cell reaction,the standard cell potential is 1.34 V.To determine the cell potential at nonstandard conditions,what is the value that should be used for n in the Nernst equation?

Accepted Answer

A)  8 
B)  10 
C)  5 
D)  2 
E)  6 
A)  8 
B)  10 
C)  5 
D)  2 
E)  6

Question 6

Which of the following is the cell notation for a voltaic cell based on the following reaction? Cu2+(aq)+ Fe(s)→ Cu(s)+ Fe2+(aq)

Accepted Answer

A)  Cu(s)| Cu2+(aq)|| Fe2+(aq)| Fe(s) 
B)  Fe(s)|| Fe2+(aq),Cu2+(aq)| Cu(s) 
C)  Cu(s)|| Cu2+(aq),Fe2+(aq)|| Fe(s) 
D)  Cu(s)| Fe2+(aq)|| Cu2+(aq)| Fe(s) 
E)  Fe(s)| Fe2+(aq)|| Cu2+(aq)| Cu(s) 
A)  Cu(s)| Cu2+(aq)|| Fe2+(aq)| Fe(s) 
B)  Fe(s)|| Fe2+(aq),Cu2+(aq)| Cu(s) 
C)  Cu(s)|| Cu2+(aq),Fe2+(aq)|| Fe(s) 
D)  Cu(s)| Fe2+(aq)|| Cu2+(aq)| Fe(s) 
E)  Fe(s)| Fe2+(aq)|| Cu2+(aq)| Cu(s)

Question 7

Which of the following reactions will require the use of an inert electrode when used in a voltaic cell?

Accepted Answer

A)  Co(s)+ 2 Ag+(aq)→ 2 Ag(s)+ Co2+(aq) 
B)  3 Ni(s)+ 2 Au3+(aq)→ 3 Ni2+ + 2 Au(s) 
C)  Cu(s)+ 2 Ag+(aq)→ Cu2+(aq)+ 2 Ag(s) 
D)  Zn(s)+ 2 MnO2(s)+ 2 NH4+(aq)→ Zn2+(aq)+ Mn2O3(s)+ 2 NH3(aq)+ H2O(l) 
E)  3 Zn2+(aq)+ 2 Al(s)→ 3 Zn(s)+ 2 Al3+(aq) 
A)  Co(s)+ 2 Ag+(aq)→ 2 Ag(s)+ Co2+(aq) 
B)  3 Ni(s)+ 2 Au3+(aq)→ 3 Ni2+ + 2 Au(s) 
C)  Cu(s)+ 2 Ag+(aq)→ Cu2+(aq)+ 2 Ag(s) 
D)  Zn(s)+ 2 MnO2(s)+ 2 NH4+(aq)→ Zn2+(aq)+ Mn2O3(s)+ 2 NH3(aq)+ H2O(l) 
E)  3 Zn2+(aq)+ 2 Al(s)→ 3 Zn(s)+ 2 Al3+(aq)

Question 8

Which of the following overall chemical equations is responsible for generating electricity in fuel cells used in NASA's Space Shuttle programs?

Accepted Answer

A)  Fe2O3(s)+ Al(s)→ Fe(s)+ Al2O3(s) 
B)  Pb(s)+ PbO2(s)+ 2 H2SO4(aq)→ 2 PbSO4(s)+ 2 H2O(   ) 
C)  2 NiO(OH)(s)+ Cd(s)+ H2O(   )→ 2 Ni(OH)2(s)+ Cd(OH)2(s) 
D)  2 H2(g)+ O2(g)→ 2 H2O(   ) 
E)  N2H4(   )+ O2(g)→ N2(g)+ 2 H2O(   ) 
A)  Fe2O3(s)+ Al(s)→ Fe(s)+ Al2O3(s) 
B)  Pb(s)+ PbO2(s)+ 2 H2SO4(aq)→ 2 PbSO4(s)+ 2 H2O(   ) 
C)  2 NiO(OH)(s)+ Cd(s)+ H2O(   )→ 2 Ni(OH)2(s)+ Cd(OH)2(s) 
D)  2 H2(g)+ O2(g)→ 2 H2O(   ) 
E)  N2H4(   )+ O2(g)→ N2(g)+ 2 H2O(   )

Question 9

The following electrochemical cell has a potential of +0.326 V at 25 °C. Pt | H2(g,1.00 atm)| H+(aq,1.00 M)|| Cl-(aq)| AgCl(s)| Ag
The standard reduction potential,E°,of AgCl(s)is +0.222 V.Calculate the Cl-(aq)ion concentration.

Accepted Answer

A)  1.9 × 10-19 M 
B)  5.5 × 10-10 M 
C)  0.018 M 
D)  1.03 M 
E)  1.8 × 109 M 
A)  1.9 × 10-19 M 
B)  5.5 × 10-10 M 
C)  0.018 M 
D)  1.03 M 
E)  1.8 × 109 M

Question 10

In the context of the diagram given below,which of the following statements is true concerning half-cell II?

Accepted Answer

A)  [Cu2+] decreases with time,and [K+] increases with time. 
B)  [Cu2+] increases with time,and [K+] increases with time. 
C)  [Cu2+] decreases with time,and [K+] decreases with time. 
D)  [Cu2+] decreases with time,and [SO42-] decreases with time. 
E)  [Cu2+] increases with time,and [SO42-] increases with time. 
A)  [Cu2+] decreases with time,and [K+] increases with time. 
B)  [Cu2+] increases with time,and [K+] increases with time. 
C)  [Cu2+] decreases with time,and [K+] decreases with time. 
D)  [Cu2+] decreases with time,and [SO42-] decreases with time. 
E)  [Cu2+] increases with time,and [SO42-] increases with time.

Question 11

Which of the following statements concerning voltaic cells is not true?

Accepted Answer

A)  A salt bridge allows cations and anions to move between half-cells. 
B)  Electrons flow from a cathode to an anode in the external circuit. 
C)  Oxidation occurs at an anode. 
D)  A voltaic cell can be used as a source of energy. 
E)  A voltaic cell consists of two half-cells. 
A)  A salt bridge allows cations and anions to move between half-cells. 
B)  Electrons flow from a cathode to an anode in the external circuit. 
C)  Oxidation occurs at an anode. 
D)  A voltaic cell can be used as a source of energy. 
E)  A voltaic cell consists of two half-cells.

Question 12

When the given oxidation-reduction reaction in an acidic solution is balanced,what is the lowest whole-number coefficient for H+,and on which side of the balanced equation should it appear? MnO4-(aq)+ Br-(aq)→ Mn2+(aq)+ Br2(l)

Accepted Answer

A)  1; reactant side 
B)  2; product side 
C)  8; reactant side 
D)  16; reactant side 
E)  4; product side 
A)  1; reactant side 
B)  2; product side 
C)  8; reactant side 
D)  16; reactant side 
E)  4; product side

Question 13

Which of the following statements is true for the following reaction,assuming the given reaction proceeds in the forward direction? 3 Sn4+(aq)+ 2 Cr(s)→ 3 Sn2+(aq)+ 2 Cr3+(aq)

Accepted Answer

A)  Sn4+(aq)is the reducing agent and Cr(s)is the oxidizing agent. 
B)  Cr(s)is the reducing agent and Sn2+(aq)is the oxidizing agent. 
C)  Sn4+(aq)is the reducing agent and Sn2+(aq)is the oxidizing agent. 
D)  Cr(s)is the reducing agent and Cr3+(aq)is the oxidizing agent. 
E)  Cr(s)is the reducing agent and Sn4+(aq)is the oxidizing agent. 
A)  Sn4+(aq)is the reducing agent and Cr(s)is the oxidizing agent. 
B)  Cr(s)is the reducing agent and Sn2+(aq)is the oxidizing agent. 
C)  Sn4+(aq)is the reducing agent and Sn2+(aq)is the oxidizing agent. 
D)  Cr(s)is the reducing agent and Cr3+(aq)is the oxidizing agent. 
E)  Cr(s)is the reducing agent and Sn4+(aq)is the oxidizing agent.

Question 14

An SHE electrode has been assigned a standard reduction potential,E°,of 0.00 volts.Which of the following reactions will occur at this electrode?

Accepted Answer

A)  2 H2O(   )+ 2 e- → H2(g)+ 2 OH-(aq) 
B)  O2(g)+ 4 e- → 2 O2-(aq) 
C)  Hg2Cl2(s)+ 2 e- → 2 Hg(   )+ 2 Cl-(aq) 
D)  Li+(aq)+ e- → Li(s) 
E)  2 H+(aq)+ 2 e- → H2(g) 
A)  2 H2O(   )+ 2 e- → H2(g)+ 2 OH-(aq) 
B)  O2(g)+ 4 e- → 2 O2-(aq) 
C)  Hg2Cl2(s)+ 2 e- → 2 Hg(   )+ 2 Cl-(aq) 
D)  Li+(aq)+ e- → Li(s) 
E)  2 H+(aq)+ 2 e- → H2(g)

Question 15

Write the balanced reduction half-reaction for the following overall reaction: 2 Fe(s)+ 3 Cl2(aq)→ 2 Fe3+(aq)+ 6 Cl-(aq)

Accepted Answer

A)  Cl2(aq)+ 2 e- → 2 Cl-(aq) 
B)  Fe(s)+ 3 e- → Fe3+(aq) 
C)  Fe(s)+ Cl2(aq)→ FeCl3(aq) 
D)  Cl2(aq)→ 2 Cl-(aq)+ 2 e- 
E)  3 Cl2(aq)+ 2 e- → 2 Cl-(aq) 
A)  Cl2(aq)+ 2 e- → 2 Cl-(aq) 
B)  Fe(s)+ 3 e- → Fe3+(aq) 
C)  Fe(s)+ Cl2(aq)→ FeCl3(aq) 
D)  Cl2(aq)→ 2 Cl-(aq)+ 2 e- 
E)  3 Cl2(aq)+ 2 e- → 2 Cl-(aq)

Question 16

For the electrochemical cell Cu(s)| Cu2+ || Ag+ | Ag(s),the standard cell potential is 0.46 V.A cell using these reagents was made,and the observed potential was 0.26 V at 25 oC.Which of the following is a possible explanation for the observed voltage?

Accepted Answer

A)  The volume of the Cu2+ solution was larger than the volume of the Ag+ solution. 
B)  The volume of the Ag+ solution was larger than the volume of the Cu2+ solution. 
C)  The Cu2+ concentration was larger than the Ag+ concentration. 
D)  The Ag electrode was twice as large as the Cu electrode. 
E)  The Ag+ concentration was larger than the Cu2+ concentration. 
A)  The volume of the Cu2+ solution was larger than the volume of the Ag+ solution. 
B)  The volume of the Ag+ solution was larger than the volume of the Cu2+ solution. 
C)  The Cu2+ concentration was larger than the Ag+ concentration. 
D)  The Ag electrode was twice as large as the Cu electrode. 
E)  The Ag+ concentration was larger than the Cu2+ concentration.

Question 17

The following has a potential of 0.34 V.   If the concentrations of each of the ions is 1.0 M and the pressure of H2 is 1.0 atm,then E° for the half-reaction   is _____.

Accepted Answer

A)  0.17 V 
B)  -0.17 V 
C)  0.34 V 
D)  -0.34 V 
E)  None of these 
A)  0.17 V 
B)  -0.17 V 
C)  0.34 V 
D)  -0.34 V 
E)  None of these

Question 18

Write a balanced half-reaction for the reduction of hydrogen peroxide to water in an acidic solution.

Accepted Answer

A)  2 H2O2(   )→ 2 H2O(   )+ O2(g) 
B)  2 H2O2(   )+ 2e- → 2 H2O(   )+ O2(g) 
C)  H2O2(   )+ 2 H+(aq)+ 2 e- → 2 H2O(   ) 
D)  H2O2(   )+ 4 H+(aq)+ 2 e- → 2 H2O(   )+ H2(g) 
E)  H2O2(   )+ 2 H+(aq)+ 4 e- → 2 H2(g)+ O2(g) 
A)  2 H2O2(   )→ 2 H2O(   )+ O2(g) 
B)  2 H2O2(   )+ 2e- → 2 H2O(   )+ O2(g) 
C)  H2O2(   )+ 2 H+(aq)+ 2 e- → 2 H2O(   ) 
D)  H2O2(   )+ 4 H+(aq)+ 2 e- → 2 H2O(   )+ H2(g) 
E)  H2O2(   )+ 2 H+(aq)+ 4 e- → 2 H2(g)+ O2(g)

Question 19

Aluminum(III)ion (Al3+)is reduced to solid aluminum at an electrode.If a current of 2.75 amperes is passed for 36 hours,calculate the mass of aluminum deposited at the electrode.(Assume 100% current efficiency.)

Accepted Answer

A)  9.2 × 10-3 g 
B)  3.3 × 101 g 
C)  9.9 × 101 g 
D)  1.0 × 102 g 
E)  3.0 × 102 g 
A)  9.2 × 10-3 g 
B)  3.3 × 101 g 
C)  9.9 × 101 g 
D)  1.0 × 102 g 
E)  3.0 × 102 g

Question 20

Calculate Ecell for the following electrochemical cell at 25 °C Pt(s)| H2(g,1.00 atm)| H+(aq,1.00 M)|| Sn2+(aq,0.350 M),Sn4+(aq,0.020 M)| Pt(s)
The standard reduction potentials are as follows:
Sn4+(aq)+ 2 e- → Sn2+(s)
E° = +0.15 V
2 H+(aq)+ 2 e- → H2(g)
E° = 0.00 V

Accepted Answer

A)  -0.19 V 
B)  +0.08 V 
C)  +0.11 V 
D)  +0.19 V 
E)  +0.22 V 
A)  -0.19 V 
B)  +0.08 V 
C)  +0.11 V 
D)  +0.19 V 
E)  +0.22 V

Exam 20: Principles of Chemical Reactivity: Electron Transfer Reactions

Write a balanced half-reaction for the reduction of CrO42-(aq)to Cr(OH)3(s)in a basic solution.

Calculate the equilibrium constant for the following reaction at 25 °C, 2 IO3-(aq)+ 5 Hg( )+ 12 H+(aq)→ I2(s)+ 5 Hg2+(aq)+ 6 H2O( ) The standard reduction potentials are as follows: IO3-(aq)+ 6 H+(aq)+ 5 e- → I2(s)+ 3 H2O( ) E° = +1.20 V Hg2+(aq)+ 2 e- → Hg( ) E° = +0.86 V

Calculate the standard cell potential ( )for the reaction 2 Ag(s)+ Co2+(aq)→ 2 Ag+(aq)+ Co(s). The standard reduction potentials are as follows: Ag+(aq)+ e−→ Ag(s) E° = 0.8 V Co2+(aq)+2 e−→ Co(s) E° = -0.277 V

Primary batteries are also called storage batteries or rechargeable batteries.

For the following cell reaction,the standard cell potential is 1.34 V.To determine the cell potential at nonstandard conditions,what is the value that should be used for n in the Nernst equation?

Which of the following is the cell notation for a voltaic cell based on the following reaction? Cu2+(aq)+ Fe(s)→ Cu(s)+ Fe2+(aq)

Which of the following reactions will require the use of an inert electrode when used in a voltaic cell?

Which of the following overall chemical equations is responsible for generating electricity in fuel cells used in NASA's Space Shuttle programs?

The following electrochemical cell has a potential of +0.326 V at 25 °C. Pt | H2(g,1.00 atm)| H+(aq,1.00 M)|| Cl-(aq)| AgCl(s)| Ag The standard reduction potential,E°,of AgCl(s)is +0.222 V.Calculate the Cl-(aq)ion concentration.

In the context of the diagram given below,which of the following statements is true concerning half-cell II?

Which of the following statements concerning voltaic cells is not true?

When the given oxidation-reduction reaction in an acidic solution is balanced,what is the lowest whole-number coefficient for H+,and on which side of the balanced equation should it appear? MnO4-(aq)+ Br-(aq)→ Mn2+(aq)+ Br2(l)

Which of the following statements is true for the following reaction,assuming the given reaction proceeds in the forward direction? 3 Sn4+(aq)+ 2 Cr(s)→ 3 Sn2+(aq)+ 2 Cr3+(aq)

An SHE electrode has been assigned a standard reduction potential,E°,of 0.00 volts.Which of the following reactions will occur at this electrode?

Write the balanced reduction half-reaction for the following overall reaction: 2 Fe(s)+ 3 Cl2(aq)→ 2 Fe3+(aq)+ 6 Cl-(aq)

For the electrochemical cell Cu(s)| Cu2+ || Ag+ | Ag(s),the standard cell potential is 0.46 V.A cell using these reagents was made,and the observed potential was 0.26 V at 25 oC.Which of the following is a possible explanation for the observed voltage?

The following has a potential of 0.34 V. If the concentrations of each of the ions is 1.0 M and the pressure of H2 is 1.0 atm,then E° for the half-reaction is _____.

Write a balanced half-reaction for the reduction of hydrogen peroxide to water in an acidic solution.

Aluminum(III)ion (Al3+)is reduced to solid aluminum at an electrode.If a current of 2.75 amperes is passed for 36 hours,calculate the mass of aluminum deposited at the electrode.(Assume 100% current efficiency.)

Calculate Ecell for the following electrochemical cell at 25 °C Pt(s)| H2(g,1.00 atm)| H+(aq,1.00 M)|| Sn2+(aq,0.350 M),Sn4+(aq,0.020 M)| Pt(s) The standard reduction potentials are as follows: Sn4+(aq)+ 2 e- → Sn2+(s) E° = +0.15 V 2 H+(aq)+ 2 e- → H2(g) E° = 0.00 V

Basic Concepts of Chemistry

Lets Review: The Tools of Quantitative Chemistry

Atoms, molecules, and Ions

Chemical Reactions

Stoichiometry: Quantitative Information About Chemical Reactions

Principles of Chemical Reactivity: Energy and Chemical Reactions

The Structure of Atoms

The Structure of Atoms and Periodic Trends

Bonding and Molecular Structure

Bonding and Molecular Structure Orbital Hybridization and Molecular Orbitals

Gases and Their Properties

Intermolecular Forces and Liquids

The Solid State

Solutions and Their Behavior

Chemical Kinetics: the Rates of Chemical Reactions

Principles of Chemical Reactivity: Equilibria

Principles of Chemical Reactivity: the Chemistry of Acids and Bases

Principles of Chemical Reactivity: Other Aspects of Aqueous Equilibria

Principles of Chemical Reactivity: Entropy and Free Energy

Environmental Chemistry: Earths Environment, energy, and Sustainability

The Chemistry of the Main Group Elements

The Chemistry of the Transition Elements

Carbon: Not Just Another Element

Biochemistry

Nuclear Chemistry

Filters

Write a balanced half-reaction for the reduction of CrO₄^2-(aq)to Cr(OH)₃(s)in a basic solution.

Calculate the standard cell potential ( )for the reaction 2 Ag(s)+ Co²⁺(aq)→ 2 Ag⁺(aq)+ Co(s). The standard reduction potentials are as follows: Ag⁺(aq)+ e⁻→ Ag(s) E° = 0.8 V Co²⁺(aq)+2 e⁻→ Co(s) E° = -0.277 V

Which of the following is the cell notation for a voltaic cell based on the following reaction? Cu²⁺(aq)+ Fe(s)→ Cu(s)+ Fe²⁺(aq)

The following electrochemical cell has a potential of +0.326 V at 25 °C. Pt | H₂(g,1.00 atm)| H⁺(aq,1.00 M)|| Cl^-(aq)| AgCl(s)| Ag The standard reduction potential,E°,of AgCl(s)is +0.222 V.Calculate the Cl^-(aq)ion concentration.

When the given oxidation-reduction reaction in an acidic solution is balanced,what is the lowest whole-number coefficient for H⁺,and on which side of the balanced equation should it appear? MnO₄^-(aq)+ Br^-(aq)→ Mn²⁺(aq)+ Br₂(l)

Which of the following statements is true for the following reaction,assuming the given reaction proceeds in the forward direction? 3 Sn⁴⁺(aq)+ 2 Cr(s)→ 3 Sn²⁺(aq)+ 2 Cr³⁺(aq)

For the electrochemical cell Cu(s)| Cu²⁺ || Ag⁺ | Ag(s),the standard cell potential is 0.46 V.A cell using these reagents was made,and the observed potential was 0.26 V at 25 ^oC.Which of the following is a possible explanation for the observed voltage?

The following has a potential of 0.34 V. If the concentrations of each of the ions is 1.0 M and the pressure of H₂ is 1.0 atm,then E° for the half-reaction is _____.

Aluminum(III)ion (Al³⁺)is reduced to solid aluminum at an electrode.If a current of 2.75 amperes is passed for 36 hours,calculate the mass of aluminum deposited at the electrode.(Assume 100% current efficiency.)

Calculate E_cell for the following electrochemical cell at 25 °C Pt(s)| H₂(g,1.00 atm)| H⁺(aq,1.00 M)|| Sn²⁺(aq,0.350 M),Sn⁴⁺(aq,0.020 M)| Pt(s) The standard reduction potentials are as follows: Sn⁴⁺(aq)+ 2 e^- → Sn²⁺(s) E° = +0.15 V 2 H⁺(aq)+ 2 e^- → H₂(g) E° = 0.00 V