EXP 11 LAB CHEM

I. Introduction

1. What is a voltaic cell and what is it consists of?
2. What type of reaction occurs in a voltaic cell?
3. What are oxidation and reduction half-reactions?
4. What is produced when the two half-reactions are connected?
5. What is a cell potential?
6. What were the objectives of this experiment?
7. What data were gathered to achieve these objectives?
8. What type of battery did you make to apply the voltaic cells concept?
9. What data were gathered from running this battery?
10. What were the hazards and what safety precautions did you implement to reduce the risk of these hazards?

II. Results Analysis

A. Data and Calculations
Refer the reader to the attached data sheet and calculations.

B. Discussion

Part I Cu-Pb Voltaic Cell
1. How was Cu-Pb Voltaic Cell set up? Show the diagram.
2. What data were obtained from the voltaic cell and what do they represent?
3. Which metal was the anode and one was the cathode?
4. What Redox reactions occurred in this voltaic cell? Show the half-reactions.
5. What was the purpose of KNO3?
6. What was the measured average cell potential of your Cu-Pb voltaic cell? Compare this value to the calculated theoretical cell potential from the textbook.
7. Why was the measured cell potential different from the textbook value?

Part II Voltaic Cell Using Pb and the Unknown Metals
1. How was the Pb-Unknown metals (X and Y) Voltaic Cell set up?
2. Which metal was the anode and one was the cathode?
3. What was the measured average cell potential of your Pb-unknown metal X voltaic cell? Compare this value to the calculated theoretical cell potential from the textbook.
4. Based on this result, what is the unknown metal X?
5. What was the measured average cell potential of your Pb-unknown metal Y voltaic cell? Compare this value to the calculated theoretical cell potential from the textbook.
6. Based on this result, what is the unknown metal Y?

Part III Making of a Soil Battery and the Light Emitting Diodes
1. What is a soil battery? What does it consist of?
2. What trend can you say about the cell potential of each soil battery cell? Briefly explain why?
3. What happened to the cell potential as you increase the number of soil battery cells connected to each other in series? Briefly explain why?
4. What LED colors did you use to test the efficiency of the soil battery you made? How did you use the soil battery to test the potential requirements of LED 1 to 5?
5. What happened to the LED as you connect each to one voltaic cell and to the voltaic cells in series
1-2, 1-2-3, and 1-2-3-4?
6. Which LED required the highest forward voltage?
7. What happened to the voltage when you connect and disconnect the LED from the voltaic cells 1-2-3-4 series?

III. Conclusions
1. What can you conclude from the results of measuring cell potential using the voltaic cells?
2. Did they give precise readings as evident from the low percent error? If yes, can you conclude that electron transfer from Redox reactions can easily be measured using these electrochemical cells?
3. Based on the unknown determination results, can you conclude that voltaic cell is a reliable way of identifying unknown metals?
4. What can you conclude from the ability of the soil battery to light up the LEDs?
5. What is the practical application of this experiment?