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CHEM3 LAB. REPORT

Electrochemical & Galvanic Cells Expt Title: : Expt#: _ Date· Performed: ----

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Section: -----.Group#: __ Date Submitted: ----Score: ------

Objective:

Procedure: A. L Add 0.5 M Cu(N03)2 to the porous cup until it is about halffull. Plac~ a clean strip of copper in the I

cup. Connect the copper electrode to the positive terminalofthe voltmeter. I 2. Add 0.5 M Zn(N03)2 to the I SOml beaker until it is about 1/3 full. Place a clean strip of zinc in the f.

beaker. Connect the zinc electrode to the negative terminal of the voltmeter. 3. Note the voltage reading of the half cells. 4. Place the porous cup in the beaker. Note the voltage reading. Remove the porous cup and return all the solutions and metal electrodes.

B. I. Assemble a galvanic cell by coupling 2 test electrodes. Dip one end of the salt bridge in one of the half cells and the other end to the second half cell. The salt bridge is thread soaked in a supersaturated KCI. The galvanic ells to be assembled involve the following pairs of electrodes: • a) Zn/Zn2+ electrode and Pb/Pb2+ electrode

2+ 2+ . b) Cu/Cu electrode and Zn/Zn electrode c) Cu/Cu2+ electrode and Pb/Pb2+ electrode

2. Connect each electrode to the input terminals of the voltmeter and read the voltage. If a negative voltage is observed, interchange the terminat'connections. Note the terminal to each electrode is connected. The cathode is the half cell connected to the positive (red) terminal of the meter, and the

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anode is the half cell connected to the negative (black) terminal. . ·

Set-up: DRAW the set- up in part A and B

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Data: Cell

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Observed E0 (V)

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:CHEM 3 LAB. REPORT ;Questions: Part A. jt. Will the c~ll operate when arranged like the firstset-up (porous cup outside the beak~r)? Explain .

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i i i 2. What is the purpose of the porous cup or salt bridge? i '

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' :\ -~ 3. What is the spontaneous half reaction taking place in the (i) Zn half cell and (ii) Cu hhlf cell ? Write the total

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1 react1on. 1 .,, .

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I I ' 4. What is the direction of electron flow in the wire connecting the zinc and copper electrodes? What is the ~irection ofthe flow of negative ions through the porous cup (or salt bridge)?

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II. Calculate the electromotive force (emt) of each galvanic cellassembled, using the s~andard electrode potentials given below

Half reaction Eu (V) Cell zn:t+ + 2e- -7 Zn -0.763 a Pb.l"' + 2e- -7 Pb -0.126 b Cu.l"' + 2e· -7 Cu 0.337 c

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2. Com

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th th 'th th b d c tpare e eore. 1ca va ue WI eo serve OmQUte ; Cell %Error

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Theoretical Eu (V) ..

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~ilnst~ad ofusing porous cup (or salt bridge) try using any citrus fruit, even banan~ . Observe if a change in potential will occur? WARNING: DO NOT EAT THE FRUIT THAT YOU'VE USED!!! . ~ .

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