Galvanic Cells Worksheet - Answer Key

 

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  1. What is a galvanic cell?

    A cell that utilizes the spontaneous electron transfer that occurs in a redox reaction to create electrical energy. 

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  2. Draw a galvanic cell and label all its components.

    3.  

     

     

  3. Why is a salt bridge necessary to complete the circuit?

    A salt bridge insures that there will not be a charge build up when the electrons transfer.                                  

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  4. What do the following acronyms mean?

      5.  

    • RED-CAT

      REDuction at CAThode

      •  

    • OX-AN

      OXidation at ANode

     

  5. What is the unit measure for cell potential?

    Volts (V) = Joule (J)

     

    Coulomb (C)

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  6. What are standard conditions?

    1M  concentration and 1 atm pressure

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  7. You must break the redox reaction into half reactions in order to determine the anode and cathode.

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  8. For a galvanic cell the value of ε°­cell must be positive as it indicates spontaneity.

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  9. What overall reaction would happen between based on the reduction potentials of each half reaction.?

      10.  

    • Mn2+ + 2e-→Mn     ε° = -1.18V

       

      Cu2++e-      →Cu             ε°=0.34V

      Mn + Cu2+→ Mn2+ + Cu               εo = 1.52V

      •  

    • Mn2+ + 2e-→Mn     ε° = -1.18V

       

      Fe3+ + 3e-      →Fe         ε° = -0.036V

      3Mn + 2Fe3+      → 3Mn2+ + 2Fe      εo = 1.14V

     

     

  10. Answer the following using standard reduction potential values

      11.  

    • Is H+(aq) capable of dissolving Cu(s) to Cu2+(aq)?

      No.

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    • Is Fe3+(aq) capable of oxidizing I-(aq)?

      Yes.

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    • Is H2(g) capable of reducing Ag+(aq)?

      Yes.

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    • Is Fe2+(aq) capable of reducing Cr3+(aq)­ to Cr2+(aq)?

      No.

     

     

  11. Using the standard reduction potential and considering

    Na+, Cl-, Ag+, Ag, Zn2+, Zn and Pb

    answer the following

      12.  

    • Which is the strongest oxidizing agent?

      Ag+

      •  

    • Which is the strongest reducing agent?

      Zn

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    • Which species can be oxidized by SO42-(aq) in acid?

      This means that any substance with a standard reduction potential less than 0.20V would be capable of being oxidized by SO42– .

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    • Which species can be reduced by Al(s)?

      This means that any substance with a standard reduction potential greater than -1.66V would be capable of oxidizing Al.

     

     

  12. What equation relates ε° and ∆G°?

    ΔGo = – nFεo

      13.  

    • What is F?

      Faraday’s Constant = 96,485    C    .
      mol e

      •  

    • What is n?

        Total moles of electrons transferred.

     

     

  13. Just as the value of  ∆G is dependent upon the concentrations of reactants/products – ε is as well.  Leading to the following equations:

      14.  

    •  For non-standard cells:

      ε = εo – RT ln Q
      nF

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    • At equilibrium:

      εo = RT ln Q
      nF

     

     

  14. Calculate the values of ∆G° and K for the following cell

    H2O2 + 2H+ + 2e-    → 2H2O             ε°= 1.78V

     

    O2 + 2H+ +2e-    → H2O2                    ε° = 0.68V

     

    ΔGo = –212,000J

     

    K = 1.62 x 1037

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  15. Consider the following galvanic cell at 25°C:

    Pt|Cr2+(0.30 M), Cr3+(2.0M)|| Co2+(0.20M)|Co                   K=2.79 x 107

    Calculate the cell potential and ∆G for this galvanic cell.    

    ε = 0.15V
    ΔG = –29,000 J  

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  16. Consider the cell described below

    Al|Al3+(1.00M)||Pb2+(1.00M)|Pb

    Calculate the cell potential after the reaction has operated long enough for the [Al3+] to have changed by 0.60 mol/L.  (assume T=25°C)

    17.  

    ε°cell = 1.50 V

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