BCE

Last modified: Wed 12/31/1969 06:00:00 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. The standard cell potential for the reaction

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

E^o = +1.10 volts. Answer the following questions about this electrochemical cell.

a) Write the half-reaction that occurs at the zinc electrode;

b) Does the mass of the zinc electrode increase, decrease or remain constant when the electrochemical cell discharges?

c) Explain why the mass changes the way you have indicated in part 1b).

2. The equilibrium constant for the reaction in Question 1 is 1.6 x 10³⁷.

a) Which direction does the reaction proceed when the electrochemical cell discharges? Left to right, right to left, or no reaction occurs.

b) Explain why the reaction proceeds in the direction you have indicated in part 2a).

3. In the table below are data collected during the discharge of the electrochemical cell.

Experiment #	[Zn²⁺] (M)	[Cu²⁺] (M)	log([Zn²⁺]/[Cu²⁺])	E^o_cell(volts)
	1.00	1.00	0	+1.100
1	1.10	0.90	0.0872	+1.097
2	1.20	0.80	0.1761	+1.095
3	1.30	0.70	0.2688	+1.092

a) What is happening to the E^o_cell going from Experiment #1 to Experiment #3?

b) What is the slope of the line when you plot E^o_cell (y-axis) versus log([Zn²⁺]/[Cu²⁺]) (x-axis). (NOTE: Copy and paste the two columns into Excel and do a 'marked scatter plot', then right click on one of the data points and add the trend line and select the option of showing the equation for the line. You have had to do this about four times in laboratory this semester.)

slope =

c) In another experiment the [Cu²⁺] = 0.357 M. What is the [Zn²⁺] in this same experiment?

[Zn²⁺] = M

d) Using the equation for the line that you obtained when you plotted the data, calculate the E^o_cell for the experiment in part 3c.

E^o_cell= volts

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

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