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EGEE 420: Fuel Cells Quizzes
N/A
155
Science
Undergraduate 3
03/14/2011

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Cards

Term
When Gibbs energy of a reaction (ΔrG) is negative, the reaction is/isn't spontaneous
Definition
is spontaneous (shifts to the right)
Term
Volume of 0.03 mol of hydrogen (as an ideal gas) at 1 bar and 25 C is ___ cm^3
Definition
(use PV=nRT)
743.6 cm^3
Term
Molecular hydrogen is oxidative/reductive/neutral
Definition
reductive
Term
Avogadro's number is ___
Definition
6.022E23
Term
25*C is ___ K
Definition
298.15 K
Term
The universal gas constant is ___
Definition
8.314 J/mol*K
0.08205 L*atm/mol*K
Term
The chemical formula of methanol is ___
Definition
CH4O
Term
If atmospheric pressure is 1 bar, the partial pressure of oxygen in air is about ___ bar
Definition
0.21 bar
Term
The redox number of oxygen in most chemical compounds is ___
Definition
-2
Term
When enthalpy of a reaction (ΔrH) is negative, the reaction is endothermal/exothermal
Definition
exothermal
Term
If hydrogen is used in a fuel cell, the output(s) is(are) ___
Definition
water, electricity, and heat
Term
How developed is the technology for the electrolytic production of hydrogen?
Definition
well developed
Term
Development of the hydrogen technology would need ___ gov't support
Definition
substantial
Term
An idea on hydrogen technology was primitively described by
Definition
Jules Verne
Term
Penn State ___ a hydrogen fuel station
Definition
already has
Term
The electrical efficiency of a fuel cell can be up to ___%
Definition
50%
Term
Molecular hydrogen ___ occurs in nature
Definition
rarely
Term
Portable fuel cell chargers are ___ on the market
Definition
already
Term
The total (electrical + heat) efficiency of a fuel cell can be up to ___%
Definition
80%
Term
Methane is an electron-___ compound
Definition
electron-precise
Term
Hydrogen is the ___ element
Definition
smallest
lightest
Term
One of the main advantages of fuel cell technology is high ___
Definition
efficiency
Term
A fuel cell can directly convert ___ of a fuel to electricity
Definition
chemical energy
Term
Fuel cell cellular phones are ___ on the market
Definition
possibly soon
Term
Hydrogen has ___ isotopes
Definition
three
Term
The range of H2 flammability in air (at 1 bar) is ___ to ___%
Definition
4 to 74%
Term
CaH2 is a ___
Definition
saline hydride
Term
The engineering principles of fuel and electrolytic cells are similar/different
Definition
very similar
Term
___ has the largest energy content per unit of weight
Definition
hydrogen
Term
H2O has ___ bonds between molecules
Definition
hydrogen bonds
Term
CrH is a ___
Definition
metallic hydride
Term
One of the main disadvantages of the fuel cell technology is ___
Definition
high cost
Term
Presently, hydrogen is mostly used for
___
Definition
ammonia production
Term
In PA, there are ___ hydrogen fuel stations
Definition
three
Term
Hydrogen and fuel cell technologies are usable/unusable for renewable energy conversion
Definition
usable
Term
The power output of a fuel cell can be
from ___ to ___
Definition
from <1 W to >1 MW
Term
The carbon-to-hydrogen ratio in methane is ___
Definition
1:4
Term
The present gov't strongly supports R&D in ___ power generation
Definition
renewable
Term
Stationary fuel cells are currently on market in what country?
Definition
Japan
Term
Ammonia is an electron-___ compound
Definition
electron-rich
Term
Hydrogen can be used to produce both ___ and ___ power
Definition
nuclear and electrical
Term
Hydrogen usually chemically/electrochemically reacts as ___
Definition
H
Term
The Honda FCX fuel cell car can be purchased/leased where?
Definition
only leased in CA
Term
The first hydrogen fuel and electrolytic cells were demonstrated by
___
Definition
Walther Nernst
Term
Cost of hydrogen produced via water electrolysis without using nuclear energy is low/high
Definition
high
Term
The U.S. Hydrogen Fuel Initiative was announced in what year?
Definition
2003
Term
Hydrogen is an energy ___
Definition
energy carrier
Term
Hydrogen can be used to (store electricity using an electrolyzer)/(produce electricity using a fuel cell)
Definition
both
Term
In a fuel cell, the cathode is ___ charged
Definition
positively
Term
Efficiency of converting electricity to hydrogen can be ___%
Definition
90%
Term
Reduction occurs at the ___
Definition
cathode
Term
A galvanic electrochemical system turns ___ into ___
Definition
chemicals into electricity
Term
Find the cell potential difference of the Daniell cell at STP if activities of Zn2+(aq) and Cu2+(aq) are, respectively, 0.1 and 0.001
Definition
!!!!! (1.041 V)
Term
H2->2 H+ + 2e- is a(n) ___ rxn
Definition
oxidation
Term
A H2/O2 PEMFC has two ___
Definition
gas electrodes
Term
Estimate the standard electrode potential at STP of the oxygen electrode, the half reaction of which is (1/2) O2(g) +2H+(aq) + 2e- = H2O(l)
Definition
!!!!!!!!!! (1.23 V)
Term
The Daniell Cell’s electrodes are what elements?
Definition
Cu and Zn
Term
Find the standard Gibbs energy (ΔrG°) of rxn of decomposition of liquid water to gaseous hydrogen and oxygen at STP
Definition
!!!!!! (+237.14 kJ/mol)
Term
The IUPAC recommendation is that the cell potential difference is left/right potential minus left/right potential
Definition
right potential - left potential
Term
The electrolyzer anode is ___ charged
Definition
positively
Term
Find the standard enthalpy (ΔrH°) of rxn of decomposition of liquid water to gaseous hydrogen and oxygen at 100 °C and 1 bar
Definition
!!!!!! (+283.454 kJ/mol)
Term
Find the standard electrode potential difference (E°) of the Daniell cell (at 25 °C) if pressure is 1000 MPa
Definition
!!!!!!! (1.097 V)
Term
An electrolytic electrochemical system
turns ___ into ___
Definition
electricity into chemicals
Term
Oxidation occurs at the ___
Definition
anode
Term
Find the standard electrode potential difference (E°) of the Daniell cell (at 1 bar) if temperature is 150 °C
Definition
!!! (1.091 V)
Term
The fuel cell anode is ___ charged
Definition
negatively
Term
A classical electrochemical cell (e.g. Daniell Cell) consists of what?
Definition
electrodes
electrolytes
salt bridge
Term
Find the standard electrode potential difference (E°) of a fuel cell that consumes hydrogen and oxygen and produces gaseous water at 1000 K and 1 bar
Definition
!!!!!!!!!! (0.998 V)
Term
Find the standard electrode potential difference (E°) of the Daniell cell (1.101 V at 25 °C) if the left-hand Zn2+/Zn electrode is replaced by the SHE
Definition
!!!!!!! (0.34 V)
Term
If Galvani potential is about 1 V, the electrochemical reaction rate can be increased by ___ orders of magnitude
Definition
a few
Term
The most common two contributions to an electrochemical reaction are ___ and ___
Definition
electron transfer
mass transfer
Term
Tafel plot can be used to experimentally estimate ___ and ___
Definition
exchange current density
transfer coefficient
Term
Concentration overpotential is related to ___
Definition
transport of the electrochemically active species
Term
Three-electrode electrochemical cell allows the study of the electrochemical kinetics of ___
Definition
the working electrode
Term
2 H+(aq) + 2e- = H2(g) is a ___ rxn
Definition
fast
Term
Based on the generalized Butler-Volmer equation, you can conclude that when the cathodic current approaches its limiting value, the overpotential goes to ___
Definition
- infinity
Term
0.5 O2(g) + 2 H+(aq) + 2e- = H2O(l) is
a ___ rxn
Definition
slow
Term
The charge transfer electrochemical kinetics is based on ___
Definition
transition state theory
Term
The net current density is defined as ___ minus ___
Definition
anodic current density minus cathodic one
Term
Using Butler-Volmer equation, calculate the current density for hydrogen half reaction at 25 °C and ovepotential of 50 mV if the exchange current density (jo) is 0.001 A/cm2 and the transfer coeff (α) is 0.5
Definition
!!!!!!! 0.002268 A/cm2
Term
When the exchange current density is 10^-2 A/cm2 the electrochemical reaction is ___
Definition
fast
Term
The exchange current density is defined when...
Definition
the anodic and cathodic currents have equal magnitude
Term
When the exchange current density is 10^-15 A/cm2 the electrochemical reaction is electrochemically reversible/irreversible
Definition
irreversible
Term
Find the concentration overpotential of the proton reduction reaction, H+(aq) + e- = (1/2) H2(g), in PEMFC at temperature of 25 °C and current density of 0.4 A/cm2 if the limiting current density is 1.1 A/cm2
Definition
!! -0.0116
Term
16. Using Tafel equation calculate the cathodic current density for oxygen half reaction at 25 oC and ovepotential of 0.8 V if the exchange current density (jo) is 10^-7 A/cm2 and the transfer coefficient (α) is 0.3
Definition
!!!!!! (+8.77E-12)
Term
Find total electrical efficiency of a fuel cell if current efficiency is 96%, voltage efficiency is 60%, and thermodynamic efficiency is 80%
Definition
take 0.96*0.60*0.80
46%
Term
If the limiting current density of a fuel cell is 1 A/cm2, the operation current density should be above/below 1 A/cm2
Definition
below 1 A/cm2
Term
As area specific resistance (Ri) increases, the fuel cell polarization curve shifts ___
Definition
down
Term
In the Daniell cell lab, when the operational mode is changed from galvanic to electrolytic, electrode polarity is ___
Definition
not changed
Term
For an electrolytic cell, magnitude of the applied voltage (potential difference) ___ magnitude of DP
Definition
>
Term
When a H2/O2 fuel cell operates at a potential difference (voltage) of 0.7 V and a current density of 0.5 A/cm2 , the power density is
Definition
!!!!!!! 0.35 W/cm2
Term
As exchange current density (io) increases, the fuel cell polarization curve shifts ___
Definition
up
Term
As operating pressure (P) increases, the fuel cell polarization curve shifts ___
Definition
up
Term
When in a H2/O2 fuel cell oxygen is replaced with air, the polarization curve shifts
Definition
down
Term
In the Daniell cell lab, when the operational mode is changed from galvanic to electrolytic, the cathode and anode ___
Definition
switch sides
Term
As transfer coefficient (alpha) increases, the fuel cell polarization curve shifts
Definition
up
Term
Calculate the charge passed through an alkaline electrolytic cell when a current of 1.8 A was constant during 3 hours
Definition
use i = dq/dt
19440 C
Term
When the amount of H2 produced in an electrolyzer is 2 L, the amount of O2 produced is ___
Definition
H2:O2 production ratio is 2:1, so 1 L
Term
For a fuel cell, the operational voltage (potential difference) ___ OCP
Definition
<
Term
Find the mass of Cu dissolved during electrolysis in Daniell cell if the process takes 30 minutes at a constant current of 0.5 A
Definition
it's a very small amount, like ~0.3 g
Term
Thermodynamic efficiency of an H2/O2 FC at 1000 K and 1 bar is ___%
Definition
!!!!!!!!!!!! 78%
Term
Thermodynamic efficiency of an ideal heat engine is defined by ___
Definition
the temp's of the hot and cold reserviors
Term
Thermodynamic efficiency of an ideal FC is defined by ___ and ___
Definition
Gibb's energy of rxn
enthalpy
Term
Thermodynamic efficiency of a C(s)/O2(g) FC that produces CO2(g) at 1000 K and 1 bar is ___
Definition
over 100%
Term
In a FC, DELTAG ___ DELTAH
Definition
can be > or <
Term
Find the standard entropy of the H2/O2 FC rxn at 400 K and 1 bar
Definition
!!!!!!!!!!!!!! -47.4 J/mol*K
Term
At 100 C and 1 bar, the standard electrode potential of H2(g)+0.5O2(g)=H2O(l) ___ that of H2(g)+0.5O2(g)=H2O(g)
Definition
about equals
Term
Find the standard Gibb's energy of a direct methanol fuel cell at STP (CH3OH(l)+1.5O2(g)=2H2O(l)+CO2(g))
Definition
!!!!!!!!!!!! -702.3 kJ/mol
Term
Thermodynamic efficiency of a combined FC-HE system can be ___%
Definition
80%
Term
Gibb's energy of a FC rxn should be ___ charged
Definition
negatively
Term
Gibb's energy of an electrolytic cell rxn should be ___ charged
Definition
positively
Term
In PEMFC, the electrodes are separated by a ___-conductive membrane
Definition
H+
Term
In PAFC the ionic conductivity is provided by ___
Definition
H+
Term
In PAFC the ion conducting electrolyte is ___
Definition
H3PO4
Term
The common operating temperature of H2/O2 PEMFC is between ___ and ___ C
Definition
50
100
Term
The temperature range which is not covered in the fuel/electrolytic cell technologies is ___ to ___ C
Definition
250
650
Term
In DMFC the anode can be made from ___
Definition
Pt-Ru alloy
Term
In SOFC the ion conductivity is provided by ___
Definition
O2-
Term
The MCFC anode is made from ___
Definition
Ni-Cr alloy
Term
The MCFC anode is made from ___
Definition
Ni and Ag
Term
The operational temperature in MCFC is between ___ to ___ C
Definition
600
700
Term
In AFC the ion-conducting electrolyte is
___
Definition
KOH
Term
AFC is intolerant to ___
Definition
CO2
Term
The operational temperature in PAFC is around ___ C
Definition
200
Term
The Nernst equation for MCFC fueled by hydrogen is...
Definition
E = EØ + (RT/2/F) ln [pH2*(pO2)^0.5 * pCO2,c / pH2O(g) / pCO2,a]
Term
The membrane thickness in PEMFCs is usually around ___
Definition
50 microns
Term
Presently, the most promising fuel cells are ___ and ___
Definition
PENFC
SOFC
Term
In PAFC the electrodes are made from ___
Definition
Pt
Term
The operational temperature in SOFC is around ___ C
Definition
900
Term
In H2/O2 PEMFC the electrodes are made from ___
Definition
Pt
Term
The SOFC anode is made from ___
Definition
Ni-based cemet
Term
The MCFC cathode is made from ___
Definition
NiO
Term
In MCFC the ion conductor is...
Definition
...a mixture of carbonates of alkali metals
Term
In MCFC the ion conductivity is provided by ___
Definition
(CO3)2-
Term
The SOFC cathode is made from ___
Definition
LaMnO3
Term
In SOFC the ion conductive membrane is
___
Definition
YSZ
Term
For the electrochemical reaction of reduction of oxygen in PEMFC at temperature below 100 °C ...
Definition
...four-phase boundary problem should be considered
Term
The SOFC can have...
Definition
planar or tubular design
Term
In PEMFC the gas diffusion layer is usually made from...
Definition
carbon cloth or carbon paper
Term
Catalysts in PEMFC are usually...
Definition
...less Pt-loaded than in PEMEC
Term
Using available for you CRC data, calculate the standard electrode potential difference , Eo, of DMFC at temperature of 50 °C
Definition
!!!!!! 1.209 V
Term
Using available for you CRC data, calculate the standard electrode potential difference, Eo, of DMFC at temperature of 150 °C
Definition
!!!!!!! 1.199 V
Term
SOFCs are ___ on the market
Definition
already
Term
In PEMFC the membrane electrode assembly (MEA) consists of...
Definition
proton conductive membrane
two electrodes
two gas diffusion layers
Term
The main components of PEMFCs or PEMECs are...
Definition
proton conductive membrane and two electrodes
gas diffusion layers and electron collector plates
Term
The typical material for PEM is ___
Definition
nafion
Term
Using available for you CRC data, calculate the electrode potential difference, E, of SOFC which uses CO and air at temperature of 900 °C and pressure of 1 bar; pure CO is the SOFC input and pure CO2 is its output; the air oxygen is completely consumed in the SOFC
Definition
!!!!! 0.880 V
Term
In H2/O2 SOFC water is produced at the ___
Definition
anode
Term
The mane difference in polarization curve of PEMFC and SOFC is due to ___
Definition
charge transfer polarization
Term
Using available for you CRC data, calculate the standard electrode potential difference, Eo, of CO/O2 SOFC at temperature of 900 °C and pressure of 1 bar
Definition
!!!!!!!!!!! 0.936 V
Term
Thermodynamic efficiency of a combined fuel cell and heat engine system is about ___%
Definition
80%
Term
Conductivity of Nafion at room temperature is around ___
Definition
0.1 S/cm
Term
In PEMFC the bipolar plates can be made from...
Definition
graphite
stainless steel
Term
In H2/O2 PEMFC water is produced at the ___
Definition
cathode
Term
Thermodynamic efficiency of a combined fuel cell and heat engine system ___ with temperature
Definition
does not change
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