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Electrochemical Cells and Cell PotentialsPeter Jeschofnig , Ph.D. Version 42-0153-00-01

L ab r e P o r t a s s i s t ant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Q ue s t i o ns P a r t i A. What half-reactions (one a reduction, the other an oxidation) can be written for this redox reaction?

B. How many electrons are being transferred from Zn (s) to Cu2+?

C. Which is the reducing agent and which is the oxidizing agent in this reaction?

D. Why does the Cu (s) produced in the redox reaction look very different from the copper metal piece?

Q ue s t i o ns P a r t ii A. Switch the multimeter on and touch the red probe (positive terminal) to the piece of copper metal and the black probe (negative terminal) to the piece of zinc metal. Read and r e c o r d the voltage. Don’t forget the sign! (Refers to Procedures Part II Step 7)

B. Reverse the probes. R e c o r d what happens to the sign and switch the meter off. (Refers toProcedures Part II Step 8)

C. Write the half-reaction occurring at the anode, Zn (s). (Refers to Procedures Part II Step 9)

D. Write the half-reaction occurring at the cathode, Cu (s). (Refers to Procedures Part II Step 10)

ox

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E. Calculate Eo , the standard oxidation potential. (Refers to Procedures Part II Step 10)

F. Calculate the equilibrium constant for the spontaneous redox reaction. (Refers to ProceduresPart II Step 11)

Q ue s t i o ns P a r t iii A. Which is the strongest oxidizing agent in the table?

B. Which is the strongest reducing agent in the table?

C. If you wanted to design a battery from relatively common materials that produced a voltage of about 1 V which cell reaction would you choose?

D. Why were the measurements on Mg (s) and Al (s) so difficult?

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ob se rvat ions Pa rt iii Refers to Procedures Part III Step 9

Data Table 1: Data MeasurementsCu red Pb red Sn red Zn red Al red

Cu blackPb blackSn blackZn blackAl blackMg black

* Pb results are most unreliable