EGEE 420 EXAMS SCRIPTED ANSWERS AND
QUESTIONS SET A+
✔✔The three reasons for polishing the metal electrodes with sand paper before
performing electrochemical measurements are to
-avoid an undesirable reaction
-provide safety
-remove the metal oxide layer
-remove the impurities
-provide faster measurement - ✔✔-avoid an undesirable reaction
-remove the metal oxide layer
-remove the impurities
✔✔The instrument to use in the Daniell Cell lab for accurate measurement of the cell
potential is
-power supply
-high impedance (resistance) electrometer
-ammeter - ✔✔high impedance (resistance) electrometer
✔✔Calculate the mass of copper dissolved during electrolysis in Daniell cell if the
charge passed through the electrode is 30.62 C.
0.0101g
1.010 g
0.101g - ✔✔0.0101g
✔✔The reaction H2O(l) → (1/2) O2(g) + H2(g) takes place in
-an electrolytic cell
-a galvanic cell
-an equilibrium cell - ✔✔an electrolytic cell
✔✔Arrange experimental procedures for the open circuit potential measurement.
, polishing electrodes
weighing electrodes
connecting electrochemical cell and electrometer
assembling the cell - ✔✔1,2,3,4
✔✔If Eø(cell) = Eø(right) -Eø(left) of an electrochemical cell is positive
-an oxidation half-reaction takes place on the right
-a reduction half-reaction takes place on the left
-a reduction half-reaction takes place on the right - ✔✔a reduction half-reaction takes
place on the right
✔✔When pressure of a fuel cell decreases, the polarization curve is
-shifting down
-not shifting
-shifting up - ✔✔shifting down
✔✔In a H2/O2 PEMFC, the cell potential decreases at low current density mainly due to
-mass transfer limitations
-internal resistance of the fuel cell
-slow electrochemical kinetics - ✔✔slow electrochemical kinetics
✔✔Use of pure oxygen instead of air in a H2/O2 PEM fuel cell
-results in a decrease in cell potential
-has no effect on cell potential
-results in an increase in cell potential - ✔✔results in an increase in cell potential
✔✔When the transfer coefficient (α) decreases, the fuel cell polarization curve is
-shifting down
-shifting up
-not shifting - ✔✔shifting down
✔✔If enthalpy of a chemical reaction is positive, the isobaric reaction is
-exothermic
-endothermic
-none of these - ✔✔endothermic
QUESTIONS SET A+
✔✔The three reasons for polishing the metal electrodes with sand paper before
performing electrochemical measurements are to
-avoid an undesirable reaction
-provide safety
-remove the metal oxide layer
-remove the impurities
-provide faster measurement - ✔✔-avoid an undesirable reaction
-remove the metal oxide layer
-remove the impurities
✔✔The instrument to use in the Daniell Cell lab for accurate measurement of the cell
potential is
-power supply
-high impedance (resistance) electrometer
-ammeter - ✔✔high impedance (resistance) electrometer
✔✔Calculate the mass of copper dissolved during electrolysis in Daniell cell if the
charge passed through the electrode is 30.62 C.
0.0101g
1.010 g
0.101g - ✔✔0.0101g
✔✔The reaction H2O(l) → (1/2) O2(g) + H2(g) takes place in
-an electrolytic cell
-a galvanic cell
-an equilibrium cell - ✔✔an electrolytic cell
✔✔Arrange experimental procedures for the open circuit potential measurement.
, polishing electrodes
weighing electrodes
connecting electrochemical cell and electrometer
assembling the cell - ✔✔1,2,3,4
✔✔If Eø(cell) = Eø(right) -Eø(left) of an electrochemical cell is positive
-an oxidation half-reaction takes place on the right
-a reduction half-reaction takes place on the left
-a reduction half-reaction takes place on the right - ✔✔a reduction half-reaction takes
place on the right
✔✔When pressure of a fuel cell decreases, the polarization curve is
-shifting down
-not shifting
-shifting up - ✔✔shifting down
✔✔In a H2/O2 PEMFC, the cell potential decreases at low current density mainly due to
-mass transfer limitations
-internal resistance of the fuel cell
-slow electrochemical kinetics - ✔✔slow electrochemical kinetics
✔✔Use of pure oxygen instead of air in a H2/O2 PEM fuel cell
-results in a decrease in cell potential
-has no effect on cell potential
-results in an increase in cell potential - ✔✔results in an increase in cell potential
✔✔When the transfer coefficient (α) decreases, the fuel cell polarization curve is
-shifting down
-shifting up
-not shifting - ✔✔shifting down
✔✔If enthalpy of a chemical reaction is positive, the isobaric reaction is
-exothermic
-endothermic
-none of these - ✔✔endothermic
