w and the concepts of electrostatic potential
energy, electric eld and electrostatic potential.
Determine
whether each statement is true or false. (Select T-True, F-
False, If the rst is T and the rest F, enter TFFFF).
A) The electric eld at a distance r from a point charge is
proportional to the charge and inversely proportional to the
square of the distance r.
B) The potential energy between two charges is positive if
the charges have opposite signs.
C) The electric eld on a circle at a distance r from a point
charge is not equal.
D) The potential energy between two charges is proportional
to the charge on each and inversely proportional to the square
of their separation.
E) The electrostatic force between two charges is positive if
the charges have opposite signs.
2.
[11-10-2004] What is the total charge of the neptunium
nucleus? (The neutral neptunium atom has 93 electrons.)
3.
[11-10-2004] What is the magnitude of its electric eld at a
distance of 2.6 �10
10
m from the nucleus?
4.
[11-10-2004] What is the magnitude of the force on an elec-
tron at that distance?
5.
[11-10-2004] What would the magnitude of the force be if
the distance of the electron from the nucleus were tripled?
6.
[11-10-2004] Calculate the potential energy of interaction
between Ca
2+
and Br separated by a distance of 1.0 nm in a
vacuum.
7.
[11-10-2004] Calculate the potential energy of interaction be-
tween Ca
2+
and Br at the same separation distance as above,
but in water. The dielectric constant of water is 74.2.
8.
[11-12-2004] Determine the ionic strength of a 0.0020 mol/kg
BaCl
2
solution.
9.
[11-12-2004] What is the activity coecient for this solu-
tion at room temperature (T = 298 K)? Again, the dielectric
constant of water is 74.2.
10.
[11-12-2004] Although it is not an ionic solute, a 0.650
mol/kg solution of boric acid, a weak acid with K
a
= 5.80 �
10
10
, is actually a weak electrolyte.
Determine the ionic
strength of this solution. Since the value of the acid equilib-
rium constant is small, you can safely assume that the amount
of dissociation of the weak acid is much smaller that the initial
concentration.
11.
[11-15-2004] Which of the following statements are true re-
garding Debye-Hueckel theory? (Give all of the correct answers,
i.e., A or BC or ABC...)
A) The Debye radius is the distance at which the screening
factor is reduced to half of its value at r=0.
B) The screening factor for a very dilute solution is approxi-
mately 1/e.
C) The potential around an ion, which is surrounded by coun-
terions, can be calculated by the ordinary Coulombs law.
D) The screening factor in the Debye-Hueckel theory is ig-
nored when counterions surround a central ion.
E) The Debye radius is the most probable distance between
a central ion and a counterion.
12.
[11-22-2004] Consider the following statements regarding
the reaction
Xe(g) + F
2
(g) XeF
4
(g)
Determine whether each statement is true or false. (Select T-
True, F-False. If the rst is T and the rest F, enter TFFFF).
A) The oxidation number of F in XeF
4
(g) is -1.
B) The oxidation number of Xe in XeF
4
(g) is 0.
C) In this reaction, Xe is oxidized.
D) The oxidation number of Xe in Xe(g) is -8.
E) The oxidation number of F in F
2
(g) is +7.
13.
[11-17-2004] Consider the following statements regarding a
standard voltaic cell with copper (+0.34 V) and zinc (-0.76 V)
electrodes. Determine whether each statement is true or false.
(Select T-True or F-False).
A) The zinc electrode undergoes oxidation.
B) In the external circuit, negative ions ow from the copper
electrode to the zinc electrode.
C) The zinc electrode serves as the positive pole of the cell.
D) The copper electrode serves as the cathode.
E) In the salt bridge, negative ions ow from the copper
electrode to the zinc electrode.
14.
[11-17-2004] Consider the following statements regarding a
standard voltaic cell with copper (+0.34 V) and silver (+0.80
V) electrodes. Determine whether each statement is true or
false. (Select T-True or F-False).
A) The copper ions undergo reduction.
B) The cell potential is -0.46 V.
C) In the external circuit, electrons ow from the anode to
the cathode.
D) The silver electrode serves as the anode.
E) The copper electrode serves as the negative pole of the
cell.
15.
[11-19-2004] Consider the following statements regarding
an electrolysis cell for coating silver with copper. The cell con-
stitutes of graphite (chemically inert at standard conditions)
and silver (+0.80 V) electrodes in a 1M CuI
2
solution. The
standard reduction potential of I
2
is +0.54 V, and of Cu
2+
is
+0.34 V. Determine whether each statement is true or false.
(Select T-True or F-False).
A) During the plating process, the copper ion concentration
decreases because metallic copper is deposited at the cathode.
B) The silver electrode serves as the positive pole in the cell.
C) The minimum potential needed to drive this process is
0.46 V.
D) The copper ions undergo reduction.
E) The graphite electrode serves as the cathode.
16.
[11-19-2004] Consider the following statements regarding
an electrolysis cell for coating silver with copper. The cell con-
stitutes of copper (+0.34 V) and silver (+0.80 V) electrodes in
a 1M CuI
2
solution. The standard reduction potential of I
2
is
+0.54 V. Determine whether each statement is true or false.
(Select T-True or F-False). A) The copper electrode serves as the anode.
B) During the plating process, copper ions are formed at the
anode and metallic copper is deposited at the cathode.
C) The minimum potential needed to drive this process is
0.46 V.
D) The copper electrode serves as the positive pole in the
cell.
E) The copper electrode undergoes oxidation.
17.
[11-19-2004] What elements are produced in the electrolysis
of LiF(aq)? Enter the names of the elements produced at the
cathode and the anode, in that order. For example, if lithium
is produced at the cathode and uorine at the anode, enter:
lithium <tab> uorine.
18.
[11-19-2004] Calculate the mass of Li produced in 8.8 hr
by the electrolysis of molten LiF if the electrical current is 6.7
A.
Complete and balance the following reaction
MnO
4
(aq) + CH
3
OH(aq) Mn
2+
(aq) + HCO
2
H(aq)
which occurs in acidic solution and answer the following
questions.
19.
[11-22-2004] Enter the elemental symbol and the change in
oxidation number of the species which is oxidized in the above
reaction. For example, if F was oxidized to F
2
, enter F and 1.
20.
[11-22-2004] Enter the elemental symbol and the change in
oxidation number of the species which is reduced in the above
reaction. For example, if F
2
was reduced to F , enter F and 1.
21.
[11-22-2004] Enter the coecients obtained for the reac-
tants. For example, if the coecient for MnO
4
(aq) is 10 and
the coecient for CH
3
OH(aq) is 15, enter 10 and 15.
22.
[11-22-2004] Enter the coecients obtained for the prod-
ucts. For example, if the coecient for Mn
2+
(aq) is 10 and the
coecient for HCO
2
H(aq) is 15, enter 10 and 15.
23.
[11-22-2004] Indicate the number and position of the proton
ions required to properly complete the equation. For example,
if 10 H
+
ions were added to the left-hand side of the equation,
enter 10 and L. If you do not have to add H
+
, enter 0 and N.
24.
[11-22-2004] Indicate the number and position of the water
groups required to properly complete the equation. For exam-
ple, if 10 H
2
O molecules were added to the right-hand side of
the equation, enter 10 and R. If you do not have to add H
2
O,
enter 0 and N.
Complete and balance the following reaction
H
2
O
2
(aq) + Cl
2
O
7
(aq) ClO
2
(aq) + O
2
(g)
which occurs in basic solution and answer the following
questions.
25.
[11-22-2004] Enter the elemental symbol and the change in
oxidation number of the species which is oxidized in the above
reaction. For example, if F was oxidized to F
2
, enter F and 1.
26.
[11-22-2004] Enter the elemental symbol and the change in
oxidation number of the species which is reduced in the above
reaction. For example, if F
2
was reduced to F , enter F and 1.
27.
[11-22-2004] Enter the coecients obtained for the reac-
tants. For example, if the coecient for H
2
O
2
(aq) is 10 and
the coecient for Cl
2
O
7
(aq) is 15, enter 10 and 15.
28.
[11-22-2004] Enter the coecients obtained for the prod-
ucts. For example, if the coecient for ClO
2
(aq) is 10 and
the coecient for O
2
(g) is 15, enter 10 and 15.
29.
[11-22-2004] Indicate the number and position of the hy-
droxl groups required to properly complete the equation. For
example, if 10 OH groups were added to the left-hand side of
the equation, enter 10 and L. If you do not have to add OH ,
enter 0 and N.
30.
[11-22-2004] Indicate the number and position of the water
groups required to properly complete the equation. For exam-
ple, if 10 H
2
O molecules were added to the right-hand side of
the equation, enter 10 and R. If you do not have to add H
2
O,
enter 0 and N.
Given are the standard reduction potentials for the two half-
reactions:
Ti
4+
(aq) + 1e Ti
3+
(aq)
E = 0.00 V
Sn
2+
(aq) + 2e Sn(s)
E = -0.14 V
31.
[11-22-2004] What would be the emf of a voltaic cell which
consists of these two standard half cells?
32.
[11-22-2004] Calculate G for the reaction:
2Ti
4+
(aq) + Sn(s) 2Ti
3+
(aq) + Sn
2+
(aq)
33.
[11-22-2004] Determine the equilibrium constant for the
above reaction at room temperature (T = 298 K).
34.
[11-17-2004]
Use
the
standard
re-
duction
potentials
posted
on
the
website
http://www.cem.msu.edu/
mantica/cem383/elec-pot.html
to determine which of the following redox reactions are
spontaneous at standard conditions. (Give all of the correct
answers, i.e., A or BC or ABC...)
A) 2Cl (aq) + I
2
(s) Cl
2
(g) + 2I (aq)