EGEE 420 COMPREHENSIVE ANSWERS AND
QUESTIONS SET A+
✔✔The two main contributions to an electrochemical reaction are
-electron (charge) transfer and adsorption/desorption
-electron (charge) transfer and mass transfer
-chemical reaction and adsorption/desorption - ✔✔electron (charge) transfer and mass
transfer
✔✔Current density is proportional to
-the concentration
-the reaction rate
-both of these - ✔✔both of these
✔✔coefficient is 0.5, the energy barrier is
-near symmetrical
-exactly symmetrical
-not symmetrical - ✔✔exactly symmetrical
✔✔Calculate the mass transfer overpotential of the proton reduction reaction, H+(aq) +
e- = 0.5 H2(g), in a PEMFC at temperature of 25 °C and current density of 0.4 A/cm2 if
the limiting current density is 1.1 A/cm2.
-0.0116 V
zero
+0.0116 V - ✔✔-0.0116 V
✔✔In three electrode electrochemical cell, the current flows between
-the working and counter electrodes
-the working and reference electrodes
-the counter and reference electrodes - ✔✔the working and counter electrodes
✔✔If transfer coefficient is approaching 1, the barrier topmost is
,-is not shifted
-shifted to the left
-shifted to the right - ✔✔shifted to the left
✔✔In the reaction profile, the activated complex is located at
-the potential energy minimum
-the potential energy maximum
-between the potential energy minimum and maximum - ✔✔the potential energy
maximum
✔✔In this course, the net current density is defined as
-cathodic current density - anodic current density
-anodic current density - cathodic current density
-anodic current density + cathodic current density - ✔✔anodic current density - cathodic
current density
✔✔When the exchange current density is 10-1A/cm2 the electrochemical reaction is
-electrochemically reversible
-electrochemically irreversible
-either reversible or irreversible - ✔✔electrochemically reversible
✔✔If the exchange current density is 10-7 A/cm2, the electrochemical reaction is
-very fast
-slow
-fast - ✔✔slow
✔✔The exchange current density is defined when there is
-no net current at an electrode
-zero overpotential
-both of these - ✔✔both of these
✔✔Galvani potential difference is
-between the bulk of metal electrode and the bulk of solution
-between the outer Helmholtz plane and the bulk of solution
-between the outer Helmholtz plane and bulk of metal electrode - ✔✔between the bulk
of metal electrode and the bulk of solution
✔✔Based on the generalized Butler-Volmer equation, we can conclude that when the
anodic current approaches its limiting value the overpotential goes to
-minus infinity
-plus infinity
-zero - ✔✔plus infinity
✔✔If the exchange current density is 10-2 A/cm2, the electrochemical reaction is
, -slow
-very slow
-fast - ✔✔fast
✔✔Using Butler-Volmer equation, calculate the current density for hydrogen half-
reaction at 25 °C and ovepotential of 30 mV if the exchange current density (jo) is 0.002
A/cm2 and the transfer coefficient (α) is 0.5.
0.0247 A/cm2
0.247 A/cm2
0.00247 A/cm2 - ✔✔0.00247 A/cm2
✔✔The charge transfer kinetics of a half-reaction is based on
-chemical kinetics
-transition state theory
-both of these - ✔✔both of these
✔✔The electrode overpotential is defined as
-the equilibrium potential between a metal electrode and the bulk solution
-electrode potential when the net current equals zero
-deviation of the Galvani potential from equilibrium potential - ✔✔deviation of the
Galvani potential from equilibrium potential
✔✔A Tafel plot can be used to experimentally estimate
-the transfer coefficient only
-the exchange current density only
-both of these - ✔✔both of these
✔✔The expression for the Faraday's law of electrolysis is
both of these
m = νi M i t i /(F ν)
m = νi Mi Q /(F ν) - ✔✔both of these
✔✔What is the power density generating of a fuel cell producing 0.5 A/cm2 at 0.7 V?
0.35 J/(cm2 s)
0.35 W/cm2
both of these - ✔✔both of these
✔✔In the Daniell cell the copper metal bar is always a positive electrode.
True
False - ✔✔true
QUESTIONS SET A+
✔✔The two main contributions to an electrochemical reaction are
-electron (charge) transfer and adsorption/desorption
-electron (charge) transfer and mass transfer
-chemical reaction and adsorption/desorption - ✔✔electron (charge) transfer and mass
transfer
✔✔Current density is proportional to
-the concentration
-the reaction rate
-both of these - ✔✔both of these
✔✔coefficient is 0.5, the energy barrier is
-near symmetrical
-exactly symmetrical
-not symmetrical - ✔✔exactly symmetrical
✔✔Calculate the mass transfer overpotential of the proton reduction reaction, H+(aq) +
e- = 0.5 H2(g), in a PEMFC at temperature of 25 °C and current density of 0.4 A/cm2 if
the limiting current density is 1.1 A/cm2.
-0.0116 V
zero
+0.0116 V - ✔✔-0.0116 V
✔✔In three electrode electrochemical cell, the current flows between
-the working and counter electrodes
-the working and reference electrodes
-the counter and reference electrodes - ✔✔the working and counter electrodes
✔✔If transfer coefficient is approaching 1, the barrier topmost is
,-is not shifted
-shifted to the left
-shifted to the right - ✔✔shifted to the left
✔✔In the reaction profile, the activated complex is located at
-the potential energy minimum
-the potential energy maximum
-between the potential energy minimum and maximum - ✔✔the potential energy
maximum
✔✔In this course, the net current density is defined as
-cathodic current density - anodic current density
-anodic current density - cathodic current density
-anodic current density + cathodic current density - ✔✔anodic current density - cathodic
current density
✔✔When the exchange current density is 10-1A/cm2 the electrochemical reaction is
-electrochemically reversible
-electrochemically irreversible
-either reversible or irreversible - ✔✔electrochemically reversible
✔✔If the exchange current density is 10-7 A/cm2, the electrochemical reaction is
-very fast
-slow
-fast - ✔✔slow
✔✔The exchange current density is defined when there is
-no net current at an electrode
-zero overpotential
-both of these - ✔✔both of these
✔✔Galvani potential difference is
-between the bulk of metal electrode and the bulk of solution
-between the outer Helmholtz plane and the bulk of solution
-between the outer Helmholtz plane and bulk of metal electrode - ✔✔between the bulk
of metal electrode and the bulk of solution
✔✔Based on the generalized Butler-Volmer equation, we can conclude that when the
anodic current approaches its limiting value the overpotential goes to
-minus infinity
-plus infinity
-zero - ✔✔plus infinity
✔✔If the exchange current density is 10-2 A/cm2, the electrochemical reaction is
, -slow
-very slow
-fast - ✔✔fast
✔✔Using Butler-Volmer equation, calculate the current density for hydrogen half-
reaction at 25 °C and ovepotential of 30 mV if the exchange current density (jo) is 0.002
A/cm2 and the transfer coefficient (α) is 0.5.
0.0247 A/cm2
0.247 A/cm2
0.00247 A/cm2 - ✔✔0.00247 A/cm2
✔✔The charge transfer kinetics of a half-reaction is based on
-chemical kinetics
-transition state theory
-both of these - ✔✔both of these
✔✔The electrode overpotential is defined as
-the equilibrium potential between a metal electrode and the bulk solution
-electrode potential when the net current equals zero
-deviation of the Galvani potential from equilibrium potential - ✔✔deviation of the
Galvani potential from equilibrium potential
✔✔A Tafel plot can be used to experimentally estimate
-the transfer coefficient only
-the exchange current density only
-both of these - ✔✔both of these
✔✔The expression for the Faraday's law of electrolysis is
both of these
m = νi M i t i /(F ν)
m = νi Mi Q /(F ν) - ✔✔both of these
✔✔What is the power density generating of a fuel cell producing 0.5 A/cm2 at 0.7 V?
0.35 J/(cm2 s)
0.35 W/cm2
both of these - ✔✔both of these
✔✔In the Daniell cell the copper metal bar is always a positive electrode.
True
False - ✔✔true
