Chapter 17 Problem
1.
A Cd/Cd2+ concentration cell is constructed in which both electrodes are pure cadmium at a
temperature of 25C. The Cd2+ concentration for one cell half is 2.0 M and for the other is 0.05
M. (a) What is the magnitude of the voltage generated between the two cells? (b) Which cell
will be oxidized: the high or low concentration cell? Enter “0” for low or “1” for high in the
space provided.
2.
An electrochemical cell is composed of pure copper and pure lead electrodes immersed in
solutions of their respective divalent ions. For a 0.3 M concentration of Cu2+, the lead electrode
is oxidized yielding a cell potential of 0.480 V. Calculate the concentration of Pb2+ ions if the
temperature is 25C. The standard potentials for Cu and Pb are +0.340 V and -0.126 V.
3.
An electrochemical cell is constructed such that on one side a pure nickel electrode is in
contact with a solution containing Ni2+ ions at a concentration of 210-3 M. The other cell half
consists of a pure Fe that is immersed in a solution of Fe2+ ions having a concentration of 0.3
M. At what temperature will the potential between the two electrodes be +0.130 V?
4.
An electrochemical cell is constructed such that on one side a pure lead electrode is in contact
with a solution containing Pb2+ ions at a concentration of 0.001 M. The other cell half consists
of a pure nickel electrode that is immersed in a solution of Ni2+ ions having a concentration of
0.4 M. Given that the standard electrode potentials for lead and nickel are -0.126 and -0.250 V,
respectively, at what temperature will the potential between the two electrodes be -0.019 V?
5.
Compute the corrosion penetration rate, in mpy, for the corrosion of iron in HCl (to form Fe 2+
ions) if the corrosion current density is 8 × 10-5 A/cm2. For iron A=55.85 g/mol and ρ=7.9
g/cm3. The following equation below may help you solve this problem:
KAi
CPR 
n
6.
Nickel experiences corrosion in an acid solution according to the reaction
Ni  2 H   Ni 2   H 2
The rates of both oxidation and reduction half-reactions are controlled by activation
polarization. (a) Compute the rate of oxidation of Ni given the following activation
polarization data:
For Nickel
For Hydrogen
VNi / Ni 2   0.250 V
VH  / H   0 V
i0 = 10-8 A/cm2
i0 = 610-7 A/cm2
 = 0.14
 = -0.11
2
(b) Compute the value of the corrosion potential.
7.
Alloys of which of the following metals may passivate?
□ copper
□ gold
□
□
□
□
titanium
chromium
iron
nickel
8.
Which of the following factors may influence the corrosion rates of materials?
□ fluid composition
□ fluid velocity
□ temperature
9.
For each of the metals listed in the table, compute the Pilling-Bedworth ratio. Also, on the
basis of this value, specify whether or not you would expect the oxide scale that forms on the
surface to be protective, and then justify your decision. Density data for both the metal and its
oxide are also tabulated.
Meatl
Metal density (g/cm3)
Metal oxide
Oxide density (g/cm3)
(a) Zr
6.51
ZrO2
5.89
(b) V
6.11
V2O5
3.36
(c) Zn
7.13
ZnO
5.61
10. In the table, weight gain-time for the oxidation of some metal at an elevated temperature are
tabulated.
W (mg/cm2)
Time (min)
1.54
10
23.24
150
95.37
620
(a) Determine whether the oxidation kinetics obey a linear, parabolic, or logarithmic rate
expression. (b) Now compute W after a time of 1500 min. Round up your answer to 3
significant digits.