35
cell voltage if Cu(NO3)2 is added to the compartment containing the Cu2+(aq)? The
cell voltage will
A) decrease.
B) increase.
C) remain the same.
D) can’t tell from the information given
123) The initial concentrations of Ag+(aq) and Cu2+(aq) are both What will happen to the
cell voltage if Cu(NO3)2 is added to the compartment containing the Cu2+(aq)? The
cell voltage will
A) decrease.
B) increase.
C) remain the same.
D) can’t tell from the information given
124) The initial concentrations of Ag+(aq) and Cu2+(aq) are both What will happen to the
cell voltage if AgNO3 is added to the compartment containing the Ag+(aq)? The cell
voltage will
A) decrease.
B) increase.
C) remain the same.
D) can’t tell from the information given
Consider the following galvanic cell.
125) What is the quantitative change in the cell voltage on increasing the ion concentration in the
anode compartment by a factor of 10?
A) +0.06 V
B) +0.03 V
C) -0.03 V
D) -0.06 V
126) What is the quantitative change in the cell voltage on increasing the ion concentration in the
cathode compartment by a factor of 10?
A) +0.06 V
B) +0.03 V
C) -0.03 V
D) -0.06 V
Consider the galvanic cell shown below.
127) What is the quantitative change in the cell voltage on increasing the ion concentration in the
anode compartment by a factor of 10?
A) +0.03 V
B) +0.02 V
C) -0.02 V
D) -0.03 V
128) What is the quantitative change in the cell voltage on increasing the ion concentration in the
cathode compartment by a factor of 10?
A) +0.03 V
B) +0.02 V
C) -0.02 V
D) -0.03 V
129) Is the cell shown above a galvanic or an electrolytic cell? Which is the anode and which is
the cathode?
A) Electolytic cell; electrode x is the anode and electrode y is the cathode.
B) Electolytic cell; electrode y is the anode and electrode x is the cathode.
C) Galvanic cell; electrode x is the anode and electrode y is the cathode.
D) Galvanic cell; electrode y is the anode and electrode x is the cathode.
130) Is the cell shown above a galvanic or an electrolytic cell? What is the direction of ion flow?
A) Electolytic cell; Cu2+ ions flow toward electrode x and SO42- ions flow toward electrode y.
B) Electolytic cell; Cu2+ ions flow toward electrode y and SO42- ions flow toward electrode x.
C) Galvanic cell; Cu2+ ions flow toward electrode x and SO42- ions flow toward electrode y.
D) Galvanic cell; Cu2+ ions flow toward electrode y and SO42- ions flow toward electrode x.
Shown below is an electrochemical cell with anode a and cathode c. Both the anode and the
cathode are inert electrodes. The liquid shown in compartment b of the cell is molten potassium
chloride, KCl(l).
131) Determine whether this is a galvanic or an electrolytic cell and give the reaction occurring
at the anode and the reaction occurring at the cathode.
A) Electrolytic cell
Anode reaction: K(s) → K+(l) + e–
Cathode reaction: Cl2(g) + 2e– → 2 Cl–(l)
B) Electrolytic cell
Anode reaction: 2 Cl–(l) → Cl2(g) + 2e–
Cathode reaction: K+(l) + e– → K(s)
C) Galvanic cell
Anode reaction: K(s) → K+(l) + e–
Cathode reaction: Cl2(g) + 2e– → 2 Cl–(l)
D) Galvanic cell
Anode reaction: K(s) → K+(l) + e–
Cathode reaction: Cl2(g) + 2e– → 2 Cl–(l)
132) Determine the direction of electron flow and the direction of ion flow.
A) Electrons flow from a to c; K+ ions flow toward a and Cl– ions flow toward c.
B) Electrons flow from a to c; Cl– ions flow toward a and K+ ions flow toward c.
C) Electrons flow from c to a; K+ ions flow toward a and Cl– ions flow toward c.
D) Electrons flow from c to a; Cl– ions flow toward a and K+ ions flow toward c.
17.2 Algorithmic Questions
1) For a galvanic cell that uses the following two half-reactions,
Cr2O72-(aq) + 14 H+(aq) + 6 e– → 2 Cr3+(aq) + 7 H2O(l)
Pb(s) → Pb2+(aq) + 2 e–
how many moles of Pb(s) are oxidized by three moles of Cr2O72-?
A) 3
B) 6
C) 9
D) 18
2) What is the reduction half-reaction for the following overall cell reaction?
Co2+(aq) + 2 Ag(s) → Co(s) + 2 Ag+(aq)
A) Ag(s) + e– → Ag+(aq)
B) Ag+(aq) + e– → Ag(s)
C) Co2+(aq) + 2 e– → Co(s)
D) Co2+(aq) + e– → Co(s)
3) What is the shorthand notation that represents the following galvanic cell reaction?
Pb(s) + Cu(NO3)2(aq) → Pb(NO3)2(aq) + Cu(s)
A) Pb(s) ∣ Pb2+(aq) ∣∣ Cu2+(aq) ∣ Cu(s)
B) Cu(s) ∣ Cu2+(aq) ∣∣ Pb2+(aq) ∣ Pb(s)
C) Pb(s) ∣ NO3–(aq) ∣∣ NO3–(aq) ∣ Cu(s)
D) Cu(s) ∣ Cu(NO3)2(aq) ∣∣ Pb(NO3)2(aq) ∣ Pb(s)
4) What is the shorthand notation that represents the following galvanic cell reaction?
2 Fe2+(aq) + F2(g) → 2 Fe3+(aq) + 2 F–(aq)
A) Fe2+(aq) ∣ Fe3+(aq) ∣∣ F2(g) ∣ F–(aq)
B) Fe(s) ∣ Fe2+(aq) ∣∣ Fe3+(aq) F2(g) ∣ F–(aq) ∣ C(s)
C) Pt(s) ∣ Fe3+(aq), Fe2+(aq), F2(g) ∣∣ F–(aq) ∣ C(s)
D) Pt(s) ∣ Fe2+(aq), Fe3+(aq) ∣∣ F2(g) ∣ F–(aq) ∣ C(s)
5) 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)
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)
6) What is the balanced chemical equation for the galvanic cell reaction expressed using
shorthand notation below?
Al(s) ∣ Al3+(aq) ∣∣ Fe2+(aq) ∣ Fe(s)
A) 2 Al(s) + 3 Fe2+(aq) → 2 Al3+(aq) + 3 Fe(s)
B) 3 Al(s) + 2 Fe2+(aq) → 3 Al3+(aq) + 2 Fe(s)
C) 2 Fe(s) + 3 Al3+(aq) → 2 Fe2+(aq) + 3 Al(s)
D) 3 Fe(s) + 2 Al3+(aq) → 3 Fe2+(aq) + 2 Al(s)
42
7) What is the balanced equation for the galvanic cell reaction expressed using shorthand
notation below?
Ni(s) ∣ Ni2+(aq) ∣∣ Cl2(g) ∣ Cl–(aq) ∣ C(s)
A) Ni(s) + 2 Cl–(aq) → Ni2+(aq) + Cl2(g)
B) Ni(s) + Cl2(g) → Ni2+(aq) + 2 Cl–(aq)
C) Ni2+(aq) + 2 Cl–(aq) → Ni(s) + Cl2(g)
D) Ni2+(aq) + 2 Cl–(aq) → NiCl2(s)
8) A galvanic cell consists of a Ni2+/Ni half-cell and a standard hydrogen electrode. If the
Ni2+/Ni half-cell standard cell functions as the anode, and the standard cell potential is 0.26 V,
what is the standard reduction potential for the Ni2+/Ni half-cell?
A) -0.26 V
B) -0.13 V
C) +0.13 V
D) +0.26 V
9) A galvanic cell consists of one half-cell that contains Ag(s) and Ag+(aq), and one half-cell
that contains Cu(s) and Cu2+(aq). What species are produced at the electrodes under standard
conditions?
Ag+(aq) + e– → Ag(s) E° = +0.80 V
Cu2+(aq) + 2 e– → Cu(s) E° = +0.34 V
A) Ag(aq) is formed at the cathode and, Cu(s) is formed at the anode.
B) Ag(s) is formed at the cathode, and Cu2+(aq) is formed at the anode.
C) Cu(s) is formed at the cathode, and Ag+(aq) is formed at the anode.
D) Cu2+(aq) is formed at the cathode, and Cu(s) is formed at the anode.
10) Consider the following standard reduction potentials,
Ni2+(aq) + 2 e– → Ni(s) E° = -0.26 V
I2(s) + 2 e– → 2 I–(aq) E° = +0.54 V
Under standard conditions,
A) Ni2+(aq) is a stronger oxidizing agent than I2(s) and I–(aq) is a stronger reducing agent than
Ni(s).
B) I2(s) is a stronger oxidizing agent than Ni2+(aq) and Ni(s) is a stronger reducing agent than I–
(aq).
C) Ni(s) is a stronger oxidizing agent than I–(aq) and Ni2+(aq) is a stronger reducing agent than
I2(s).
D) I–(aq) is a stronger oxidizing agent than Ni(s) and I2(s) is a stronger reducing agent than
Ni2+(aq).
11) Based on the following information,
Cl2(g) + 2 e– → 2 Cl–(aq) E° = +1.36 V
Mg2+(aq) + 2 e– → 2 Mg(s) E° = -2.37 V
which of the following chemical species is the strongest reducing agent?
A) Cl2(g)
B) Mg2+(aq)
C) Cl–(aq)
D) Mg(s)
12) Calculate ΔG° for the following galvanic cell Zn(s) ∣ (aq) ∣∣ (aq) ∣Fe(s) given these
reduction potentials:
(aq) + 2 →Zn(s) E° = -0.76 V
(aq) + 2 → Fe(s) E° = -0.45 V
A) -59.8 kJ
B) 59.8 kJ
C) -29.8 kJ
D) 29.8 kJ
13) Using the following standard reduction potentials,
Fe3+(aq) + e– →Fe2+(aq) E° = +0.77 V
Cd2+(aq) + 2 e– →Cd(s) E° = -0.40 V
calculate the standard cell potential for the cell reaction given below, and determine whether or
not this reaction is spontaneous under standard conditions.
Cd2+(aq) + 2 Fe2+(aq) → 2 Fe3+(aq) + Cd(s)
A) E° = –1.17 V, nonspontaneous
B) E° = -1.17 V, spontaneous
C) E° = +1.17 V, nonspontaneous
D) E° = +1.17 V, spontaneous
14) Consider the galvanic cell, Which one of the following
changes to the cell would cause the cell potential to increase (i.e., become more positive)?
A) increase the [Zn2+] concentration
B) increase the [Pb2+] concentration
C) increase the mass of Zn(s)
D) decrease the mass of Zn(s)
15) Calculate the value of the reaction quotient, Q, for the galvanic cell expressed using
shorthand notation below.Use the balanced chemical equation that has the smallest, whole
number stoichiometric coefficients.
Zn(s) ∣ Zn2+(aq, 0.0100 M) ∣∣ Ag+(aq, 1.15 M) ∣ Ag(s)
A) 132
B) 115
C) 8.70 × 10-3
D) 7.56 × 10-3
16) The equilibrium constant, K, for a redox reaction at 25° C is 3.3 × . What is the value of
E° if the overall reaction transfers 2 electrons?
A) 0.93 V
B) 1.9 V
C) 2.2 V
D) 0.60 V
17) 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?
A) 27.6 g
B) 49.2 g
C) 82.4 g
D) 248 g
18) How many grams of nickel metal are plated out when a constant current of 15.0 A is passed
through aqueous NICl2 for 60.0 minutes?
A) 10.9 g
B) 16.4 g
C) 32.8 g
D) 36.3 g
19) How long must a constant current of 50.0 A be passed through an electrolytic cell containing
aqueous Cu2+ ions to produce 5.00 moles of copper metal?
A) 0.187 hours
B) 0.373 hours
C) 2.68 hours
D) 5.36 hours
17.3 Short Answer Questions
1) A galvanic cell uses the reaction
Mg(s) + Pb2+(aq) → Mg2+(aq) + Pb(s).
Mg(s) → Mg2+(aq) + 2 e– is the ________ half-reaction, which occurs at the ________.
2) In the galvanic cell represented by the shorthand notation
Al(s)|Al3+(aq)||Fe3+(aq)|Fe(s)
the anode is ________ and the cathode is ________.
3) For the galvanic cell that uses the reaction
2 Al(s) + 3 Zn2+(aq) → 2 Al3+(aq) + 3 Zn(s)
the value of n in the relationship △G° = – nFE° is ________.
4) Reduction half-reactions with corresponding standard half-cell potentials are shown below.
Zn2+(aq) + 2 e– → Zn(s) E° = – 0.76 V
Al3+(aq) + 3 e– → Al(s) E° = – 1.66 V
The standard potential for the galvanic cell that uses these two half-reactions is ________ V.
5) Reduction half-reactions with corresponding standard half-cell potentials are shown below.
Ag+(aq) + 1 e– → Ag(s) E° = + 0.80 V
Zn2+(aq) + 2 e– → Zn(s) E° = – 0.76 V
Al3+(aq) + 3 e– → Al(s) E° = – 1.66 V
Of the species above, the strongest oxidizing agent is ________, and the strongest reducing agent
is ________.
6) The standard cell potential for the following galvanic cell is 1.21 V.
Al(s)|Al3+(aq)||Fe2+(aq)|Fe(s)
When [Al3+] = 0.10 M and [Fe2+] = 0.10 M, will the cell potential at 25°C be less than, the
same as, or greater than 1.21 V?
7) The standard reduction potential Eo = – 0.45 V for the half-reaction Fe2+ + 2 e– → Fe. If the
measured cell potential at 25°C is 0.35 V, the pH in the anode compartment of the following cell
is ________.
Pt(s)|H2(1 atm)|H+(? M)||Fe2+(1 M)|Fe(s)
8) The standard cell potential for the following galvanic cell is 0.71 V.
Mg(s)|Mg2+(aq)||Al3+(aq)|Al
This reaction has an equilibrium constant, K = ________.
9) The two half-reactions that are used in the direct methanol fuel cell are shown below.
I 2 CH3OH(aq) + 2 H2O(l) → 2 CO2(g) + 12 H+(aq) + 12 e–
II 3 O2(g) + 12 H+(aq) + 12 e– → 6 H2O(l)
The electrode at which half-reaction I occurs is the ________ at which ________ is oxidized,
and half-reaction II occurs at the ________ at which ________ is reduced.
10) If a constant current of 1.50 × 108 A is passed through a molten mixture of aluminum oxide
and cryolite for 4.00 hour ________ kg of aluminum can be produced.