Last modified: Mon 10/21/2013 10:44:17 pm
BCE

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Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.

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For this BCE we will use this short version of the Standard Reduction Potential Table. You might want to print the table out before beginning the BCE.

1. Calculate the standard cell potential for the reaction

Zn(s) + Cu2+(aq) ----> Zn2+(aq) + Cu(s)

Eo = volts

2. Write the equilibrium expression for the reaction in Question 1. (Remember how we handle substances in the solid phase.)

K = (Remember this expression is also equal to Q)

3. When we prepare an electrochemical cell using standard conditions the concentration of ions is 1 M at 298 K. When we measure the voltage the reaction is not at equilibrium. Calculate the value of Q for the reaction when the electrochemical half cells is first connected and the concentrations of all ions is 1.00 M.

Q =

4. Based on the value of Eo is this reaction thermodynamically favored? (Y/N)

5. What is the value of K for the reaction in Question 1.

(Go = -nFEo where F = 96,500 J volt-1

and Go = -RT ln K where R = 8.314 J mol-1 K-1

so Eo = RT/nF ln K or Eo = 0.0257/n ln K

n is the number of electrons transferred in the balanced chemical equation)

K =

6. Suppose we prepared an electrochemical cell based on the same reaction, but instead of 1 M Zn2+ we made the [Zn2+]=0.1 M and we'll leave the [Cu2+]=1.0 M. Use Dr. Greenbowe's Flash animation to measure the cell potential for this electrochemical cell.

E = volts

7. Use the equation

Ecell = Eo - (0.0592/n) log [Zn2+]/[Cu2+]

(NOTE: n = # of electrons transferred)

calculate Ecell for the reaction. How does your calculated value compare to the measured value.

8. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

9. If there is one question you would like to have answered in lecture, what would that question be?