EGEE 441 E4
In an electrolytic cell, the signs of the exchange current density (jo) and current density (j) are: [Note:see table 8.1 p168]
A) + and -, respectively
B) - and -, respectively
C) - and +, respectively
D) + and +, respectively
In a PEMFC, water is
A) consumed at the cathode
B) produced at the cathode
C) produced at the anode
D) consumed at the anode
If the total, voltage, and current efficiencies are, respectively, 40%, 50%, and 95%, the thermodynamic efficiency of an electrochemical energy conversion system (without heat exchange) is
A) 93%
B) 85%
C) 95%
D) 84%
Cation conductive membranes are used in [Note: DMFC is a type of PEMFC]
A) PEMFC
B) DMFC
C) both of these
The metal dissolution half-reaction in a corrosion process is
A) either anodic or cathodic reaction
B) an anodic reaction
C) a cathodic reaction
If a hydrogen/oxygen generation [H2O(l) = H2(g) + 0.5 O2(g), E0 = -1.229V] electrolytic cell operates at 25 C under the following parameters for the potential-current density equation (AEC = 0.1V, BEC = 0.04 V, j0 = 0.001 A/cm^2, jp = 0.02 A/cm^2, jlim = -0.9 A/cm^2, rEC = 0.4 ohm cm^2), calculate the potential difference (cell voltage) when the electrolysis current density is (I) 0 A/cm^2 and (II) -0.2 A/cm^2.
A) (I) -1.53 V, (II) -1.86 V
B) (I) 0.93 V, (II) 0.37 V
C) (I) -0.53 V, (II) -1.69 V
D) (I) -1.53 V, (II) -2.09 V
The cathodic protection of Fe(s) against electrochemical corrosion, Fe(s) = Fe2 + 2 e-, can be provided using
A) none of these
B) Cu
C) Cd
Corrosion can not be decreased by
A) passivation
B) cathodic protection
C) trans-passivation
Immunity of Cu(s) at ambient conditions in an acidic solution at pH = 2 can be achieved at
A) Eh > 0.3 V
B) Eh < 0.3 V
C) any Eh
Which of these fuel cells requires platinum as a catalyst?
A) SOFC
B) PEMFC
C) AFC
What is the molar Gibbs energy of H2/O2 PEMFC reaction written as 2 H2(g) + O2(g) = 2 H2O(l), if the standard electrode potential difference is 1.2 V?
A) -463.13 kJ/mol
B) -115.85 kJ/mol
C) -451.55 kJ/mol
D) -231.65 kJ/mol
Using data from Chapter 10: Data Section, calculate the standard thermodynamic efficiency of a CO2/O2 electrolytic cell at 800 K [CO2(g) = C(s) + O2(g)].
A) 99.64 %
B) 100.41 %
C) 88.35 %
D) 99.66 %
When the entropy of an electrochemical reaction in a fuel or an electrolytic cell is negative, a part of the total available energy will be ____________ in the form of heat.
A) either consumed or released
B) released from the reaction
C) consumed by the reaction
Corrosion resistance of a metal is considered poor if the corrosion rate is [Note; p181 Table 9.1]
A) 0.04 mm/y
B) 4 mm/y
C) 0.4 mm/y
If the corrosion current is 0.02 mA/cm^2, the corrosion rate of copper (M = 63.55 g/mol, p = 8.96 g/cm^3) due to Cu(s) -> Cu2+ (aq) + 2 e- reaction is _____. (Hint: 365.2 day/year)
A) 0.580 mm/year
B) 0.358 mm/year
C) 5.80 mm/year
D) 0.232 mm/year
In an fuel cell, the signs of the limiting current density and parasitic current density are
A) - and +, respectively
B) + and +, respectively
C) - and -, respectively
D) + and -, respectively
As temperature increases in a fuel cell, the charge transfer resistance
A) increases
B) decreases
C) stays the same
If the current density in a corrosion process 0.05 A/cm^2 and the overpotential is 200 mV, the area specific corrosion polarization resistance is [Note:eq9.4 pg179]
A) 200 ohm cm^2
B) 4 ohm cm^2
C) 0.2 ohm cm^2
D) 20 ohm cm^2
For the corrosion process with two-electron half-reactions at 25 C, if the overpotential from Ecorr is 10 mV and the measured current density response is 5 mA/cm^2, with the anodic and cathodic symmetry coefficients, respectively, 0.75 and 0.25, the corrosion current density, jcorr using the Stern Geary equation is [Note: p179-180]
A) 3.11 mA/cm^2
B) 9.21 mA/cm^2
C) 3.21 mA/cm^2
D) 6.42 mA/cm^2
Corrosion of Al(s) in aerated water is likely to take place at [Note: p177 Fig. 9.2]
A) pH > 9
B) pH < 4
C) both of these
The fuel cell was invented by
W. Nernst
M. Faraday
C. F. Schönbein
The fuel cell was discovered in
20th century
19th century
18th century
Aqueous KOH solution is used as electrolyte in
AFC
SOFC
PEMFC
DMFC is a kind of
SOFC
PEMFC
AFC
An anion conductive membrane is used in
PEMFC
SOFC
DMFC
In DMFC water is
Consumed at the anode
Produced at the cathode
Both of these
Carbon monoxide can be used as a fuel in
SOFC
PEMFC
DMFC
At ambient temperature and pressure, for the PEMFC cathode, the main challenge to be addressed is the
Four-phase boundary problem
Three-phase boundary problem
Two-phase boundary problem
At ambient pressure and temperature above 100 °C, for the PEMFC cathode, the main challenge to be addressed is the
four-phase boundary problem
Two-phase boundary problem
Three-phase boundary problem
In PEMFC, the electrolyte is
An ion conductive ceramic membrane
An ion conductive polymeric membrane
An ion conductive aqueous solution
Using data from Chapter 10: Data Section, estimate the standard value of the Gibbs energy of an H2/O2 PEMFC [H2(g) + (1/2) O2(g) = H2O(g)] at 1000 K.
-228.6 kJ/mol
-164.4 kJ/mol
-192.6 kJ/mol
Using data from Chapter 10: Data Section, calculate the standard value of the decomposition potential (DP) of the H2O electrolysis [H2O(l) = H2(g) + (1/2) O2(g)] at 100 °C.
+1.167 V
-1.167 V
-1.229 V
Using data from Chapter 10: Data Section, the standard thermodynamic efficiency of a C/O2 fuel cell [C(s) + O2(g) = CO2(g)] at 900 K is
= 100 %
> 100 %
< 100 %
Using data from Chapter 10: Data Sections, calculate the voltage efficiency of a C/O2 fuel cell [C(s) + O2(g) = CO2(g)] at 1000 K when the fuel cell potential is 0.5 V and all activities equal 1.
49 %
55 %
41 %
If the thermodynamic, voltage, and current efficiencies are, respectively, 93, 51, and 95 %, the total efficiency of an electrochemical energy conversion system (without heat exchange) I
55 %
45 %
Using the following parameters of the potential-current density equation (AFC = 0.08 V, BFC = 0.05 V, jo = 0.001 A/cm2, jp = 0.01 A/cm2 , jlim = 1.0 A/cm2, rFC = 0.2 Ω cm2) for a H2/O2 PEMFC, [H2(g) + (1/2) O2(g) = H2O(l), 25 °C] calculate the cell potential, EFC, at (I) 0 A/cm2 and (II) 0.7 A/cm2 with all species at unit activity.
(I) 1.045 V and (II) 0.705 V
(I) 1.229 V and (II) 0.505 V
(I) 1.045 V and (II) 0.504 V
The fuel cell was developed by
W. Grove
W. Nernst
M. Faraday
In a water electrolyzer at ambient conditions and at low current, the heat is
Neither realized nor consumed
consumed
Released
In a H2/O2 fuel cell at ambient conditions and at low current, the amount of heat released due to electrochemical reactions is about
38.7 kJ/mol
58.7 kJ/mol
48.7 kJ/mol
Using data from Chapter 10: Data Section, calculate the standard thermodynamic efficiency of a water electrolyzer at ambient conditions.
83 %
120 %
100 %
The Flade potential is due to metal
Transpassivation
Activation
Passivation
The electrochemical corrosion involves
a cathodic reaction
both of these
An anodic reaction
In an electrochemical corrosion process, the current of the anodic and cathodic reactions should be
Equal
Zero
Different
In an electrochemical corrosion measurement
the corrosion potential can be measured
Both of these
The corrosion current can be measured
To correctly study a metal corrosion rates, the electrochemical cell should have
three electrodes
two electrodes
either of these
The current density in the passive region of a corrosion polarization curve is
Zero
Small
Large
If the corrosion current is 0.1 mA/cm2, the corrosion rate of iron due to Fe(s) → Fe2+(aq) + 2 e- reaction is
0.0116 mm/year
0.116 mm/year
1.16 mm/year
The potential-pH (Pourbaix) diagram can
be used to approximately estimate the corrosion rate
Be used to estimate the corrosion rate
Not be used to estimate the corrosion rate
Immunity of Al(s) at ambient conditions in pure water can be achieved at Eh
< -1.9 V
> -1.9 V
< 0 V
In the Cu(s) Pourbaix diagram, the line corresponding to Cu2+(aq) + 2 H2O(l) = Cu(OH)2(s) + 2 H+(aq) reaction is
Horizontal
Vertical
inclined
In the Cu(s) Pourbaix diagram, the line corresponding to Cu2+(aq) + 2 e– = Cu(s) half-reaction is
Horizontal
Inclined
Vertical
In the Cu(s) Pourbaix diagram, the line corresponding to Cu2O(s) + 2 H+(aq) + 2 e- = 2 Cu(s) + H2O(l) half-reaction is
Horizontal
Inclined
Vertical
When pH = 0 and temperature is 25 °C, the oxygen reduction line [2 H+(aq) + (1/2) O2(g) + 2 e- = H2O(l)] in the Pourbaix diagram intersects the Eh axis at
1.23 V
- 1.23 V
0 V
When pH = 7 and temperature is 25 °C, the hydrogen evolution line [2 H+(aq) + 2 e- = H2(g)] in the Pourbaix diagram intersects the Eh axis at
about -0.4 V
About -0.8 V
About 0.0 V
Mitigation of corrosion can be provided by
forming a protective film
Electrochemical cathodic protection
Both of these
If Zn(s) and Fe(s) are galvanically coupled, the metal to be corroded is Chapter 9: Electrochemical Corrosion & Chapter 4: Equilibrium Electrochemistry
Zn(s)
Both of these
Fe(s)
The cathodic protection of Cu(s) can be provided, if Cu(s) is galvanically connected to
Ag(s)
Zn(s)
Au(s)
In any Pourbaix diagram, a line can represent
a mass action law equation
a Nernst’s equation
Either of these
To calculate the corrosion current,
Tafel constants should be known
Both of these should be known
The corrosion polarization resistance should be known
Transpassivation occurs due to
Either of these
Another anodic electrochemical reaction
Breakdown of a passive film
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