0581.5271 – “Electrochemistry for Engineers”
HOMEWORK #1
Question #1 (32 pts)
a) On the above plot, draw and label the line representing the lower stability of water (6pts)
b) On the above plot, draw and label the line representing the upper stability of water (6pts)
c) In what pH region, if possible, can you deposit manganese (Mn) without producing hydrogen bubbles?
If it is possible, label this region on the graph above (10 pts)
d) In what pH region, if possible, can Mn+2 by oxidized to manganese oxide (MnO2) without forming
oxygen bubbles? If it is possible, label this region on the graph. (10pts)
Question 2 (34pts)
POLARIZATION CURVES for Cu Electrode
POLARIZATION CURVES for Cr Electrode
Cell Diagram
a) Fill in the standard reduction potentials for the cell above in the cell diagram. What is the open circuit
potential of the cell assuming the cell is spontaneous? (3 pts)
b) In the cell diagram draw the direction of electrons if you wanted to dissolve copper and deposit
chromium. Is this type of cell galvanic (if so, connect the cell and draw a lightbulb) or electrolytic (if so,
connect the cell and draw a battery)? (3 pts)
c) Using the blank graphs for the polarization curves provided above, draw polarization curves for both
the chromium and copper electrode assuming activation control only, with a symmetry factor is 0.5 and
the exchange current density is “low”. Label the anodic ovepotential (∆Ea1) and cathodic overpotential
(∆Ec1) for the cell operating in electrolytic mode at 1 mA. (10 pts)
d) Draw a second set of polarization curves for both chromium and copper (preferably in a different
color) assuming the same activation control and symmetry factor but assuming the exchange current
density is much higher for both electrodes compared to part (c). Label the overpotentials (∆Ea2) and
(∆Ec2) for the anode and cathode respectively for the cell operating in electrolytic mode at 1 mA. (10
pts)
e) If this cell were to run in an electrolytic mode at 1 mA, would we want a high exchange current or a
low exchange current at each electrode in order to minimize the overpotential? (8 pts)
Question 3) 33 pts (PLEASE USE SNOOK ET AL TO ANSER THESE QUESTIONS)
Liquid Junction Potentials (LJP) are present whenever 2 dissimilar liquids come into contact.
When 2 different ionic liquids are brought into contact, an LJP is inevitably formed.
1) Can a liquid junction potential be physically measured? Why or why not?
2) What physical parameters are used to calculate the liquid junction potential between 2
dissimilar liquids
3) Why is the Ferrocene redox couple (Fc/Fc+) commonly used as an internal reference for nonaqueous systems?
4) Refer to table 2 and Figure 3. Why is the LJP between L14TFSI and AmmoEng 100 positive
and why is the LJP between L14TFSI and the remaining ionic liquids negative?