Electrochemistry Problem Set

1. Calculate the cell potential and free energy available for the following electrochemical systems.
   1. Ag(s)|Ag¹⁺(aq 1.0 M)||Cu²⁺ (aq 1.0 M)|Cu(s)
   2. Ag(s)|Ag¹⁺(aq 0.1 M)||Cu²⁺ (aq 0.1 M)|Cu(s)
   3. Ag(s)|Ag¹⁺(aq 1.0 M)||Cu²⁺ (aq 0.1 M)|Cu(s)
   4. Ag(s)|Ag¹⁺(aq 1.0 M)||Cu²⁺ (aq 0.01M)|Cu(s)
   5. Ag(s)|Ag¹⁺(aq 0.1 M)||Cu²⁺ (aq 1.0 M)|Cu(s)
   6. Cu(s|Cu²⁺ (aq 1.0 M)||Ag¹⁺(aq 1.0 M)|Ag(s))

2. If the electrochemical cell discussed is used as a battery and begins with 10.0 g electrodes (silver and copper), and 250 mL of each 1.0 M solution.
   1. Identify the limiting reagent in the reaction.
   2. Calculate the number of moles of electrons exchanged when the reaction goes to completion.

3. Batteries are frequently made using solid electrodes. What advantage might this provide?

4. Tin cans are very common. Answer the following questions based upon the diagram of the electrochemical cell shown below:
   1. What is missing in the cell as it is drawn here? What effect does this have on the rusting of a tin can?
   2. After the cell is complete, what is E^o_cell. Which side of the can is the anode, and which is the cathode.
   3. Write out all the relevant half reactions for this system.
   4. In real life, the concentrations are not likely to be the same as under standard conditions. If it is a hot summer day (98 °F), and the [Fe²⁺] in contact with the cell is 1.35*10^-5 M, and the [Sn²⁺] is 8.41*10^-3 M, what is the cell potential.

5. On space craft, a H2, O2 fuel cell is used to produce electricity.
   1. The reactions
      1. What is the reaction at the anode?
      2. What is the reaction at the cathode?
      3. What is the balanced redox reaction?
      4. What is Ecell assuming P_o2 = 2*atm, and P_H2 = 2*atm.

   2. If two cylinders of H2 and 1 cylinder of O2 (cylinder: volume=200 liter, pressure = 3000 psi) are used.
      1. How many moles of electons can be produced?
      2. How much energy (joules) is this?
      3. If this energy has to last for 1 week, what is the average power (watts) available?

   3. Compare the amount of energy produced by this fuel cell to the energy produced by the combustion of the same amount of H2 and O2 using Hrxn.

   4. The following relationships may be useful:
      1. V = kg m² s^-3 A
      2. A = C s^-1
      3. J = kg m² s^-2
      4. W = J s^-1

   5. Electrochemical Analysis techniques are capable of detecting very small amounts of certain metals. In one type of analysis Cd²⁺ undergoes electrolysis. In this experiment it is possible to detect a signal from 1 pA of current, lasting only 1 ms.
      1. How many moles of Cd²⁺ does this correspond to?
      2. How many atoms is this?

   ---

   Please send comments or suggestions to svanbram@science.widener.edu

   Scott Van Bramer
   Department of Chemistry
   Widener University
   Chester, PA 19013

   © copyright 1996, S.E. Van Bramer
   This page has been accessed times since 1/5 /96 .

   Last Updated: Saturday, May 18, 1996