ADDIS ABABA UNIVERSITY

ADDIS ABABA INSTITUTE OF TECHNOLOGY
SCHOOL OF CHEMICAL AND BIO ENGINEERING

Applied Electrochemistry WORKSHEET -1

1. Calculate the standard potential of each of the following cells. State which one(s), if any, will proceed spontaneously as written.
a. Sn + Pb2+ Sn2+ + Pb
b. Zn+ Pb2+ Zn2+ + Pb

2. Calculate the potential of each of the following:
(a) 2 Ag(s) + Fe2+ (0.100 M) 2 Ag+ (0.100 M) + Fe(s)

3. Calculate the emf at 298 K generated by a voltaic cell in which the reaction is

Cr2O72- (aq) + 14 H+(aq) + 6 I-(aq) 2 Cr 3+ (aq) + 3 I2(s) + 7 H2O(l)

[ Cr2O72- ] = 2.0 M [H+] = 1.0 M [I-] = 1.0 M [Cr3+] = 1.0 * 10-5 M

4. The Ksp at 298 K for iron(II) fluoride is 2.4 x10-6 .
a. Write a half-reaction that gives the likely products of the two-electron reduction of FeF2(s) in water.
b. Use the Ksp value and the standard reduction potential of Fe 2+ to calculate the standard reduction potential for the half-reaction in part (a).
c. Rationalize the difference between the reduction potential in part (a) and the reduction potential for Fe 2+.

5. Can we store copper sulphate in (i)Zinc vessel (ii) Silver vessel? Give reasons.
Given E0 Cu2+/Cu = +0.34V, E0Zn2+/Zn= -0.76V) , E0Ag+/Ag = +0.80V

6. Elemental calcium is produced by the electrolysis of molten CaCl2. (a) What mass of calcium can be produced by this process if a current of 7.5 * 103A is applied for 48 h? Assume that the electrolytic cell is 68% efficient. (b)What is the minimum voltage needed to cause the electrolysis?

7. (a) How many coulombs are required to plate a layer of chromium metal 0.25 mm thick on an auto bumper with a total area of 0.32 m2 from a solution containing CrO42? The density of chromium metal is 7.20 g/cm3 . (b) What current flow is required for this electroplating if the bumper is to be plated in 10.0 s? (c) If the external source has an emf of and the electrolytic cell is 65% efficient, how much electrical power is expended to electroplate the bumper?

8. Calculate the number of kilowatt-hours of electricity required to produce 1.0 * 103 kg (1 metric ton) of aluminum by electrolysis of Al 3+ if the applied voltage is 4.50 V and the process is 45% efficient.
9.

Please follow the directions on the Post a New Question page (see below, too) -- indicate what YOU HAVE DONE to solve each of these. Then a chemistry tutor might help.

Homework Posting Tips

Please show your work. Tutors will not do your homework for you. Please show your work for any question that you are posting.

To calculate the standard potential of each of the cells and solve the other electrochemistry problems, you'll need to use the Nernst equation and other related concepts. Here's a step-by-step guide on how to approach each problem:

1. For cell potentials:
a. Write the balanced cell equation for each cell:
- Cell 1: Sn + Pb2+ → Sn2+ + Pb
- Cell 2: Zn + Pb2+ → Zn2+ + Pb
b. Determine the standard reduction potential (E°) for each half-reaction involved in the cells. You can find these values in a standard reduction potential table.
c. Use the Nernst equation to calculate the standard potential (E°cell) for each cell:
- E°cell = E°cathode - E°anode
d. Determine which cell(s) will proceed spontaneously as written:
- If E°cell is positive, the cell will proceed spontaneously.

2. For potential calculation:
a. Write the balanced cell equation for the given reaction:
- 2 Ag(s) + Fe2+ (0.100 M) → 2 Ag+ (0.100 M) + Fe(s)
b. Determine the standard reduction potential for each half-reaction involved.
c. Use the Nernst equation to calculate the potential:
- Ecell = E°cell - (0.0592/n) log(Q)
- Q = [Ag+]^2/[Fe2+]

3. For cell EMF calculation:
a. Write the balanced cell equation for the given reaction:
- Cr2O72- (aq) + 14 H+(aq) + 6 I-(aq) → 2 Cr 3+ (aq) + 3 I2(s) + 7 H2O(l)
b. Determine the standard reduction potential for each half-reaction involved.
c. Use the Nernst equation to calculate the cell EMF at 298 K:
- Ecell = E°cell - (0.0592/n) log(Q)
- Q = [Cr^3+]^2/[I-]^6[H+]^14

4. For Ksp and reduction potential calculation:
a. Write the half-reaction for the two-electron reduction of FeF2(s) in water.
b. Use the Ksp value and the standard reduction potential of Fe2+ to calculate the standard reduction potential for the mentioned half-reaction.
c. Rationalize the difference between the obtained reduction potential in part (a) and the reduction potential for Fe2+.

5. To determine if copper sulfate can be stored in different vessels:
- Compare the reduction potentials (E°) of Cu2+/Cu, Zn2+/Zn, and Ag+/Ag to determine if any of the metals (Zinc, Silver) would react with Copper sulfate.

6. For electrolysis calculation:
a. Use Faraday's Law to calculate the mass of calcium produced:
- Mass = (current × time × molar mass / Faraday's constant) × efficiency
b. To find the minimum voltage needed, use Faraday's Law:
- Voltage = (current × time / Faraday's constant) × efficiency

7. For electroplating calculation:
a. Determine the amount of coulombs required:
- Coulombs = Current × Time
b. Calculate the required current flow for electroplating:
- Current = Coulombs / Time
c. Calculate the electrical power expended:
- Power = Voltage × Current × Efficiency

8. For electricity required to produce aluminum:
- Use Faraday's Law, efficiency, and the applied voltage to calculate the number of coulombs required.
- Convert the coulombs to kilowatt-hours.

Note: Make sure you have the necessary values for molar masses, Faraday's constant, and other relevant constants to perform the calculations accurately.