Section 21.1
Voltaic Cells
Practice Test
1.
Which of the following must be true of a salt bridge?
a.
Ions can move through the salt bridge.
b.
The salt bridge must prevent the flow of charged particles.
c.
The solutions joined by the salt bridge can mix freely.
d.
The tube of the salt bridge must remain open.
Hint
2.
In any electrochemical cell, the cathode is the ________.
a.
positive electrode
b.
negative electrode
c.
electrode at which some species gains electrons
d.
electrode at which some species loses electrons
Hint
3.
In a voltaic cell, the salt bridge __________.
a.
is not necessary for the cell to work
b.
acts as a mechanism to allow mechanical mixing of the solutions
c.
allows charge balance to be maintained in the cell
d.
drives electrons from one half-cell to another
Hint
4.
A cell is constructed by immersing a strip of lead in a 1.0
M
Pb(NO
3
)
2
solution and a strip of silver in a 1.0
M
AgNO
3
solution. The circuit is completed by a wire and a salt bridge. As the cell operates, the strip of silver gains mass (only silver), the strip of lead loses mass, and the concentration of lead ions increases in the solution around the lead strip. Which of the following represents the reaction that occurs at the cathode in this cell?
a.
Pb
2+
+ 2e
-
→ Pb
b.
Pb → Pb
2+
+ 2e
-
c.
Ag
+
+ e
-
→ Ag
d.
Ag → Ag
+
+ e
-
Hint
5.
Using a table of standard reduction potentials, which of the following is the strongest oxidizing agent?
a.
Al
3+
b.
Al
c.
F
2
d.
F
-
Hint
6.
Which of the following is the weakest reducing agent?
a.
Al
3+
b.
Al
c.
F
2
d.
F
-
Hint
7.
A voltaic cell consists of a standard hydrogen electrode connected by a salt bridge and a wire to an electrode consisting of a strip of Cd metal dipping into a 1
M
solution of Cd(NO
3
)
2
. When the cell produces a current, the electrons flow through the wire from the _________ electrode to the ________ electrode. In this cell, the _______ electrode acts as the cathode.
a.
Cd, H
2
, Cd
b.
H
2
, Cd, Cd
c.
H
2
, Cd, H
2
d.
Cd, H
2
, H
2
Hint
8.
Under standard conditions, what is the standard cell potential for the cell? Cd|Cu
2+
|| Cu
2+
|Cu?
a.
+0.74 V
b.
-0.74 V
c.
0.06 V
d.
-0.06 V
Hint
9.
Under standard conditions, which of the following is the net reaction that occurs in the cell? Cd|Cd
2+
|| Cu
2+
|Cu
a.
Cu + Cd
2+
→ Cd + Cu
2+
b.
Cu + Cd → Cu
2+
+ Cd
2+
c.
Cu
2+
+ Cd
2+
→ Cu + Cd
d.
Cu
2+
+ Cd → Cu + Cd
2+
Hint
10.
What is the numerical value for the standard cell potential for the following reaction? 2Cr
3+
(aq) + 3Cu(s) → 2Cr(s) + 3Cu
2+
(aq)
a.
-1.08 V
b.
-0.40 V
c.
0.40 V
d.
1.08 V
Hint
11.
How many moles of electrons have been transferred between the species in the following reaction? 2Cr
3+
(aq) + 3Cu(s) → 2Cr(s) + 3Cu
2+
(aq)
a.
2
b.
3
c.
4
d.
6
Hint
12.
A voltaic cell in which the reaction involves the combustion of one reactant with oxygen to produce electric energy is a(n) _____________.
a.
primary battery
b.
secondary battery
c.
fuel cell
d.
electrolytic cell
Hint
