Consider the following galvanic cell.
132) 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
133) 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.
134) 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
135) 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
136) Is the cell shown above a galvanic or an electrolytic cell? Which is the anode and which is the
cathode?
A) Electrolytic cell; electrode x is the anode and electrode y is the cathode.
B) Electrolytic 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.
137) Is the cell shown above a galvanic or an electrolytic cell? What is the direction of ion flow?
A) Electrolytic cell; Cu2+ ions flow toward electrode x and SO42- ions flow toward electrode y.
B) Electrolytic 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).
138) 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)
139) 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 mol es 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)
38
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)
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) Using the following standard reduction potentials,
Fe3+(aq) + e– → Fe2+(aq) E° = +0. 77 V
Ni2+(aq) + 2 e– →Ni(s) E° = -0.26 V
calculate the standard cell potential for the cell reaction given below, and determine whether or not this
reaction is spontaneous under standard conditions.
Ni2+(aq) + 2 Fe2+(aq) → 2 Fe3+(aq) + Ni(s)
A) E° = – 1.03 V, nonspontaneous
B) E° = – 1.03 V, spontaneous
C) E° = + 1.03, nonspontaneous
D) E° = + 1.03, spontaneous
13) Consider the galvanic cell, Zn(s) ∣ Zn2+(aq) ∣∣ Pb2+(aq) ∣ Pb(s). 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)
14) 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
15) The gas OF2 can be produced from the electrolysis of an aqueous solution of KF, as shown in the
equation below.
OF2(g) + 2 H+(aq) + 4 e– → H2O(l) + 2 F–(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.
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.
16) 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
17) 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
18) 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) In the galvanic cell represented by the shorthand notation shown below
Pb(aq) | Pb2+(aq) | Cl2(g)|Cl–(aq) | Pt(s)
the inert electrode is ________, and the balanced cathode half-reaction reaction is ________.
4) In the shorthand notation for a galvanic cell, a single vertical line (|) represents a ________, and a
double vertical line (||) represents a ________.
5) In the galvanic cell represented by the shorthand notation below, electrons are lost by ________ and
gained by ________.
Pt(s) | Sn2+(aq) | Sn4+(aq) || Br2(l)|Br–(aq) | Pt(s)
6) The galvanic cell represented by the shorthand notation below contains KNO3(aq) in the salt bridge.
During the reaction ________ ions flow into the anode compartment, and ________ ions flow into the
cathode compartment.
Pt(s)|H2(g)|H+(aq) || Sn4+(aq)|Sn2+(aq)|Pt(s)
7) 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 ΔG° = –nFE° is ________.
8) For the hypothetical reaction A + Bx → Ax + B, E° = 1.30 V and ΔG° = -251 kJ. For this reaction the
value of x = ________.
9) For the hypothetical reaction 3 A + 2 Bx → 3 Ay + 2 B, E° = 0.85 V and G° = -495 kJ. For this
reaction the values of x and y are ________ and ________.
10) In order for a cell potential to be a standard cell potential, the concentration of all ions in solution
must be ________ M, the partial pressures of all gaseous species must be ________ atm, and the
temperature must be ________ K.
11) 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.
12) Based on the half-reactions and their respective standard reduction potentials below, the standard
cell potential for the reaction that is expected to occur is ________ V.
Ag+(aq) + e– → Ag(s) 0.80 V
2 H+(aq) + 2 e– → H2(g) 0.00 V
Cd2+(aq) + 2 e– → Cd(s) -0.40 V
13) 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
________.
14) Based on the half-reactions and their respective standard reduction potentials below, the strongest
reducing agent is ________, and the strongest oxidizing agent is ________.
Fe3+(aq) + 3 e– → Fe2+(aq) 0.77 V
Sn4+(aq) + 2 e– → Sn2+(aq) 0.15 V
Pb2+(aq) + 2 e– → Pb(s) -0.13 V
15) 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?
16) The standard reduction potential E° = –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)
17) 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 = ________.
18) 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.
19) 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.
20) Electrolysis of a metal nitrate solution M(NO3)2(aq) for 3.00 hours with a constant current of 20.0
A gives 119 g of the metal M. The identity of the metal M in the metal ion M2+ is ________.