Question 1

Predict the species that will be reduced first if a mixture of molten salts containing the following ions undergoes electrolysis: Zn2+, Fe3+, Mg2+, Br-, I-

Accepted Answer

A) Zn2+ 
B) Mg2+ 
C) Br- 
D) Fe3+ 
E) I- 
A) Zn2+ 
B) Mg2+ 
C) Br- 
D) Fe3+ 
E) I-

Question 2

For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs at the cathode? Zn(s)∣ Zn2+(aq)∣∣ Ni2+(aq)∣ Ni(s)

Accepted Answer

A) Zn(s)→ Zn2+(aq)+ 2 e- 
B) Zn2+(aq)+ 2 e- → Zn(s) 
C) Ni(s)→ Ni2+(aq)+ 2 e- 
D) Ni2+(aq)+ 2 e- → Ni(s) 
A) Zn(s)→ Zn2+(aq)+ 2 e- 
B) Zn2+(aq)+ 2 e- → Zn(s) 
C) Ni(s)→ Ni2+(aq)+ 2 e- 
D) Ni2+(aq)+ 2 e- → Ni(s)

Question 3

How many seconds are required to produce 4.00 g of aluminum metal from the electrolysis of molten AlCl3 with an electrical current of 12.0 A?

Accepted Answer

A) 27.0 
B) 9.00 
C) 1.19 × 103 
D) 2.90 × 105 
E) 3.57 × 103 
A) 27.0 
B) 9.00 
C) 1.19 × 103 
D) 2.90 × 105 
E) 3.57 × 103

Question 4

What element is being oxidized in the following (unbalanced)redox reaction? Cr(OH)4⁻(aq)+ ClO⁻(aq)→ CrO42-(aq)+ Cl⁻(aq)

Accepted Answer

A) Cr 
B) O 
C) H 
D) Cl 
A) Cr 
B) O 
C) H 
D) Cl

Question 5

Explain the significance of the standard hydrogen electrode (SHE)in the tabulation of standard reduction potentials of other species.

Accepted Answer

The SHE is used to construct an electroc

Question 6

Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25 °:
Fe(s)∣ Fe3+(aq, 0.0011 mol L-1)   Fe3+(aq, 2.33 mol L-1)∣ Fe(s)
E°(Fe3+/Fe)= -0.036 V

Accepted Answer

A) +0.066 V 
B) -0.036 V 
C) 0.00 V 
D) -0.099 V 
E) +0.20 V 
A) +0.066 V 
B) -0.036 V 
C) 0.00 V 
D) -0.099 V 
E) +0.20 V

Question 7

The gas OF2 can be produced from the electrolysis of an aqueous solution of KF, as shown in the equation below: OF2(g)+ 2H+(aq)+ 4 e- → H2O(l)+ 2F-(aq)E° = +2.15 V
Using the given standard reduction potential, calculate the amount of OF2 that is produced, and the electrode at which the OF2 is produced, upon the passage of 0.480 faradays through an aqueous KF solution.

Accepted Answer

A) 6.48 g of OF2 at the anode 
B) 26.0 g of OF2 at the anode 
C) 6.48 g of OF2 at the cathode 
D) 26.0 g of OF2 at the cathode 
A) 6.48 g of OF2 at the anode 
B) 26.0 g of OF2 at the anode 
C) 6.48 g of OF2 at the cathode 
D) 26.0 g of OF2 at the cathode

Question 8

Which of the following statements is TRUE?

Accepted Answer

A) A reduction process corresponds to an increase in oxidation state as a result of loss of electrons. 
B) An oxidation process involves the loss of electrons resulting in an increase in oxidation state. 
C) An oxidation process corresponds to a decrease in oxidation state as a result of a gain of electrons. 
D) During a reduction process electrons are lost, while during an oxidation they are gained. 
E) During a reduction process an oxidation state increases, while in an oxidation process an oxidation state decreases. 
A) A reduction process corresponds to an increase in oxidation state as a result of loss of electrons. 
B) An oxidation process involves the loss of electrons resulting in an increase in oxidation state. 
C) An oxidation process corresponds to a decrease in oxidation state as a result of a gain of electrons. 
D) During a reduction process electrons are lost, while during an oxidation they are gained. 
E) During a reduction process an oxidation state increases, while in an oxidation process an oxidation state decreases.

Question 9

For a galvanic cell that uses the following two half-reactions, Cr2O72-(aq)+ 14H+(aq)+ 6 e- → 2Cr3+(aq)+ 7H2O(l)
Pb(s)→ Pb2+(aq)+ 2 e-
How many moles of Pb(s)are oxidized by three moles of Cr2O72-?

Accepted Answer

A) 3 
B) 6 
C) 9 
D) 18 
A) 3 
B) 6 
C) 9 
D) 18

Question 10

Which of the following metals will dissolve in nitric acid but not hydrochloric acid?

Accepted Answer

A) Fe; Eo(Fe2+/Fe)= -0.45V 
B) Pb; Eo(Pb2+/Pb)= -0.13V 
C) Cu; Eo(Cu2+/Cu)= +0.34V 
D) Sn; Eo(Sn2+/Sn)= -0.14V 
E) Ni; Eo(Ni2+/Ni)= -0.23V 
A) Fe; Eo(Fe2+/Fe)= -0.45V 
B) Pb; Eo(Pb2+/Pb)= -0.13V 
C) Cu; Eo(Cu2+/Cu)= +0.34V 
D) Sn; Eo(Sn2+/Sn)= -0.14V 
E) Ni; Eo(Ni2+/Ni)= -0.23V

Question 11

Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 °C.

Accepted Answer

A) Pb2+(aq)+ Cu(s); if Eo(Pb2+/Pb)= -0.13V and Eo(Cu2+/Cu)= +0.16V 
B) Ag+(aq)+ Br⁻(aq); if Eo(Ag+/Ag)= 0.80V and Eo(Br2/Br-)= +1.09V 
C) Li+(aq)+ Al(s); if Eo(Li+/Li)= -3.04V and Eo(Al3+/Al)= -1.66V 
D) Fe3+(aq)+ Ni(s); if Eo(Fe3+/Fe)= -0.04V and Eo(Ni2+/Ni)= -0.23V 
E) Cd2+(aq)+ I-(aq); if Eo(Cd2+/Cd)= -0.40V and Eo(I2/I-)= + 0.54V 
A) Pb2+(aq)+ Cu(s); if Eo(Pb2+/Pb)= -0.13V and Eo(Cu2+/Cu)= +0.16V 
B) Ag+(aq)+ Br⁻(aq); if Eo(Ag+/Ag)= 0.80V and Eo(Br2/Br-)= +1.09V 
C) Li+(aq)+ Al(s); if Eo(Li+/Li)= -3.04V and Eo(Al3+/Al)= -1.66V 
D) Fe3+(aq)+ Ni(s); if Eo(Fe3+/Fe)= -0.04V and Eo(Ni2+/Ni)= -0.23V 
E) Cd2+(aq)+ I-(aq); if Eo(Cd2+/Cd)= -0.40V and Eo(I2/I-)= + 0.54V

Question 12

Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br2 and OH⁻ in the balanced reaction? Br2(l)→ BrO3⁻(aq)+ Br⁻(aq)

Accepted Answer

A)  Br2 = 1, OH⁻ = 2 
B)  Br2 = 2, OH⁻ = 5 
C)  Br2 = 3, OH⁻ = 3 
D)  Br2 = 3, OH⁻ = 6 
E)  Br2 = 1, OH⁻ = 6 
A)  Br2 = 1, OH⁻ = 2 
B)  Br2 = 2, OH⁻ = 5 
C)  Br2 = 3, OH⁻ = 3 
D)  Br2 = 3, OH⁻ = 6 
E)  Br2 = 1, OH⁻ = 6

Question 13

Which of the following reactions would have the smallest value of K at 298 K?

Accepted Answer

A) A + B → C; E°cell = +1.22 V 
B) A + 2 B → C; E°cell = +0.98 V 
C) A + B → 2 C; E°cell = -0.030 V 
D) A + B → 3 C; E°cell = +0.15 V 
E) A + B → C; E°cell = -0.015 V 
A) A + B → C; E°cell = +1.22 V 
B) A + 2 B → C; E°cell = +0.98 V 
C) A + B → 2 C; E°cell = -0.030 V 
D) A + B → 3 C; E°cell = +0.15 V 
E) A + B → C; E°cell = -0.015 V

Question 14

Why are iron nails coated with zinc?

Accepted Answer

Zinc is more easily oxidized t

Question 15

What element is being reduced in the following (unbalanced)redox reaction? MnO4⁻ (aq)+ H2C2O4(aq)→ Mn2+(aq)+ CO2(g)

Accepted Answer

A) C 
B) O 
C) Mn 
D) H 
A) C 
B) O 
C) Mn 
D) H

Question 16

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al(s)+ 3I2(s)→ 2Al3+(aq)+ 6I-(aq)
The emf generated by the cell when [Al3+] = 4.5 × 10-3 mol L-1 and [I-] = 0.15 mol L-1 is

Accepted Answer

A) 2.20 
B) 2.32 
C) 2.10 
D) 2.39 
E) 2.23 
A) 2.20 
B) 2.32 
C) 2.10 
D) 2.39 
E) 2.23

Question 17

Match the following.

-ΔrG° > 0

Accepted Answer

A) E°cell cell cell > 0 
D) Ecell > 0 
E) Ecell = 0
F)Ecell = E°cell 
A) E°cell cell cell > 0 
D) Ecell > 0 
E) Ecell = 0
F)Ecell = E°cell

Question 18

Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 °C.

Accepted Answer

A) I-(aq)+ Zn2+(aq); if Eo(I2/I-)= + 0.54V and Eo(Zn2+/Zn)= -0.76V 
B) Ca(s)+ Mg2+(aq); if Eo(Ca2+/Ca)= -2.76V and Eo(Mg2+/Mg)= -2.37V 
C) H2(g)+ Cd2+(aq); if Eo(Cd2+/Cd)= -0.40V 
D) Ag(s)+ Sn2+(aq); if Eo(Ag+/Ag)= + 0.80V and Eo(Sn2+/Sn)= -0.14V 
E) Ag+(aq)+ Mn2+(aq); if Eo(Ag+/Ag)= + 0.80V and Eo(MnO4-/Mn2+)= +1.51V 
A) I-(aq)+ Zn2+(aq); if Eo(I2/I-)= + 0.54V and Eo(Zn2+/Zn)= -0.76V 
B) Ca(s)+ Mg2+(aq); if Eo(Ca2+/Ca)= -2.76V and Eo(Mg2+/Mg)= -2.37V 
C) H2(g)+ Cd2+(aq); if Eo(Cd2+/Cd)= -0.40V 
D) Ag(s)+ Sn2+(aq); if Eo(Ag+/Ag)= + 0.80V and Eo(Sn2+/Sn)= -0.14V 
E) Ag+(aq)+ Mn2+(aq); if Eo(Ag+/Ag)= + 0.80V and Eo(MnO4-/Mn2+)= +1.51V

Question 19

Describe how water can be made to be a good conductor of electrical current.

Accepted Answer

A) use pure water 
B) heat the water 
C) add salt 
D) chill the water 
E) vaporize the water 
A) use pure water 
B) heat the water 
C) add salt 
D) chill the water 
E) vaporize the water

Question 20

How many grams of chromium metal are plated out when a constant current of 8.00 A is passed through an aqueous solution containing Cr3+ ions for 320. minutes?

Accepted Answer

A) 27.6 g 
B) 49.2 g 
C) 82.4 g 
D) 248 g 
A) 27.6 g 
B) 49.2 g 
C) 82.4 g 
D) 248 g

Exam 18: Electrochemistry

Predict the species that will be reduced first if a mixture of molten salts containing the following ions undergoes electrolysis: Zn2+, Fe3+, Mg2+, Br-, I-

For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs at the cathode? Zn(s)∣ Zn2+(aq)∣∣ Ni2+(aq)∣ Ni(s)

How many seconds are required to produce 4.00 g of aluminum metal from the electrolysis of molten AlCl3 with an electrical current of 12.0 A?

What element is being oxidized in the following (unbalanced)redox reaction? Cr(OH)4⁻(aq)+ ClO⁻(aq)→ CrO42-(aq)+ Cl⁻(aq)

Explain the significance of the standard hydrogen electrode (SHE)in the tabulation of standard reduction potentials of other species.

Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25 °: Fe(s)∣ Fe3+(aq, 0.0011 mol L-1) Fe3+(aq, 2.33 mol L-1)∣ Fe(s) E°(Fe3+/Fe)= -0.036 V

Which of the following statements is TRUE?

For a galvanic cell that uses the following two half-reactions, Cr2O72-(aq)+ 14H+(aq)+ 6 e- → 2Cr3+(aq)+ 7H2O(l) Pb(s)→ Pb2+(aq)+ 2 e- How many moles of Pb(s)are oxidized by three moles of Cr2O72-?

Which of the following metals will dissolve in nitric acid but not hydrochloric acid?

Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 °C.

Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br2 and OH⁻ in the balanced reaction? Br2(l)→ BrO3⁻(aq)+ Br⁻(aq)

Which of the following reactions would have the smallest value of K at 298 K?

Why are iron nails coated with zinc?

What element is being reduced in the following (unbalanced)redox reaction? MnO4⁻ (aq)+ H2C2O4(aq)→ Mn2+(aq)+ CO2(g)

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al(s)+ 3I2(s)→ 2Al3+(aq)+ 6I-(aq) The emf generated by the cell when [Al3+] = 4.5 × 10-3 mol L-1 and [I-] = 0.15 mol L-1 is

Match the following. -ΔrG° > 0

Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 °C.

Describe how water can be made to be a good conductor of electrical current.

How many grams of chromium metal are plated out when a constant current of 8.00 A is passed through an aqueous solution containing Cr3+ ions for 320. minutes?

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Predict the species that will be reduced first if a mixture of molten salts containing the following ions undergoes electrolysis: Zn²⁺, Fe³⁺, Mg²⁺, Br^-, I^-

For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs at the cathode? Zn(s)∣ Zn²⁺(aq)∣∣ Ni²⁺(aq)∣ Ni(s)

How many seconds are required to produce 4.00 g of aluminum metal from the electrolysis of molten AlCl₃ with an electrical current of 12.0 A?

What element is being oxidized in the following (unbalanced)redox reaction? Cr(OH)₄⁻(aq)+ ClO⁻(aq)→ CrO₄^2-(aq)+ Cl⁻(aq)

Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25 °: Fe(s)∣ Fe³⁺(aq, 0.0011 mol L^-1) Fe³⁺(aq, 2.33 mol L^-1)∣ Fe(s) E°(Fe³⁺/Fe)= -0.036 V

For a galvanic cell that uses the following two half-reactions, Cr₂O₇^2-(aq)+ 14H⁺(aq)+ 6 e^- → 2Cr³⁺(aq)+ 7H₂O(l) Pb(s)→ Pb²⁺(aq)+ 2 e^- How many moles of Pb(s)are oxidized by three moles of Cr₂O₇^2-?

Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br₂and OH⁻ in the balanced reaction? Br₂(l)→ BrO₃⁻(aq)+ Br⁻(aq)

What element is being reduced in the following (unbalanced)redox reaction? MnO₄⁻ (aq)+ H₂C₂O₄(aq)→ Mn²⁺(aq)+ CO₂(g)

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al(s)+ 3I₂(s)→ 2Al³⁺(aq)+ 6I^-(aq) The emf generated by the cell when [Al³⁺] = 4.5 × 10^-3 mol L^-1 and [I^-] = 0.15 mol L^-1 is

Match the following. -Δ_rG° > 0

How many grams of chromium metal are plated out when a constant current of 8.00 A is passed through an aqueous solution containing Cr³⁺ ions for 320. minutes?