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EGEE 441 EXAM 2 QUESTIONS AND ANSWERS FULLY SOLVED
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Exam of 11 pages for the course EGEE at EGEE (EGEE 441 EXAM 2)
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EGEE 441 EXAM 2The Gibbs energy of formation of any chemical element in its reference state is
-≠0
- none of these
- = 0 - answer= 0
Absolute value of the Galvani potential difference (electrical potential difference
between two phases)
- is known
- can be thermodynamically calculated
- is unknown - answer is unknown
When temperature increases, the standard OCP of a H2/O2 fuel cell
- decreases
- does not change
- increases - answer decreases
If one uses data of Chapter 10: Data Section, it can be found that when temperature
increase, the standard Gibbs energy of C(s)/O2(g) fuel cell reaction
- does not change
- decreases
- increases - answer decreases
If a fuel cell reaction is (1/2) CH4(g) + O2(g) = (1/2)CO2(g) + H2O - answer
If a fuel cell reaction is (1/2)CH4(g) + O2(g) = (1/2)CO2(g) + H2O(g), the standard
Gibbs energy of the reaction is defined as
- ΔfGo(H2O,g) + 0.5 ΔfGo(CO2,g)
- 0.5 ΔfGo(CH4,g) - ΔfGo(O2,g)
- ΔfGo(H2O,g) + 0.5 ΔfGo(CO2,g)
+ 0.5 ΔfGo(CH4,g) + ΔfGo(O2,g)
- ΔfGo(H2O,g) + ΔfGo(CO2,g) -
ΔfGo(CH4,g) - ΔfGo(O2,g) - answerΔfGo(H2O,g) + 0.5ΔfGo(CO2,g) - 0.5 ΔfGo(CH4,g)
- ΔfGo(O2,g)
The precise relationship between Gibbs energy (ΔrG), enthalpy (ΔrH), and entropy
(ΔrS) of a chemical reaction at temperature T is
- ΔrG(T) = ΔrH(T) - T ΔrS(T)
- ΔrG(T) = ΔrH(To) - T ΔrS(To), where To = 298.15 K
- ΔrG(T) = ΔrH(T) + T ΔrS(T) - answerΔrG(T) = ΔrH(T) - T ΔrS(T)
, If a fuel cell reaction is H2(g) + (1/2) O2(g) = H2O(g), the Nernst equation (at low
pressure) can be written as
- E = E0 ± [RT/(2F)] ln[(pH2 )(pO20.5)/pH2O]
- E = E0 - [RT/(2F)] ln[(pH2 )(pO20.5)/pH2O]
- E = E0 + [RT/(2F)] ln[(pH2 )(pO20.5)/pH2O] - answerE = E0 + [RT/(2F)] ln[(pH2 )
(pO20.5)/pH2O]
The absolute entropy of any chemical is
-=0
->0
- < 0 - answer> 0
The following half-reaction takes place at the oxygen gas electrode: (1/2) O2(g) + 2 H+
(aq) + 2 e- = H2O(l). If one uses data from Chapter 10: Data Section, the standard
electrode potential corresponding to this half-reaction at 100 °C and 1 bar is
- 1.067 V
- 1.167 V
- 1.267 V - answer1.167 V
In a carbon (graphite)/oxygen fuel cell the cathodic reaction is O2(g) + 4 e- = 2 O2- and
the anodic one is CO2(g) + 4 e- = C(s) + 2 O2-. If one uses data from Chapter 10: Data
Section, the standard electrode potential difference of the fuel cell at 1000 K and 1 bar
is
- 1.226 V
- 1.126 V
- 1.026 V - answer1.026 V
What is the OCP of the H2(g)/Cl2(g) electrochemical cell [Pt(s)|H2(g)|HCl(aq)|Cl2(g)|
Pt(s)] at 25 oC, if partial pressure of hydrogen and chlorine are 0.5 bar and the
concentration of HCl(aq) is 5 mol/kg?
- 1.426 V
- 1.358 V
- 1.213 V - answer1.213 V
Calculate the open circuit potential of a Daniell cell (at 25 oC and 1 bar) with ZnSO4(aq,
0.01 mol/kg ) on the left hand side and CuSO4(aq, 0.002 mol/kg) on the right hand side
if the ionic activity coefficients of Cu2+(aq) and Zn2+(aq) are, respectively, 0.658 and
0.392.
- 1.088 V
- 1.102 V
- 1.117 V - answer1.088 V
A person body can approximately be considered as
- in equilibrium state
- none of these
- in steady state - answerin steady state
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