Electrochemical Cells

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Oxidation-reduction reactions are second fundamental type of chemical reaction. Redox reactions as they are often called are simply reactions that involve the transfer of electrons from one chemical species to another. This electron transfer will obviously shift the ratio of the protons to electrons on the atoms involved and will thus affect the oxidation number of the atoms involved. Atoms that gain electrons are said to have been reduced (their oxidation number goes down) and atoms that have lost electrons are said to have been oxidized.

The energy released in a spontaneous redox reaction can be used to do electrical work. This is accomplished using a voltaic cell, a device in which the transfer of electrons occurs through an external pathway rather than directly between reactants.

To illustrate and construct galvanic cells of different metal electrodes and measuring the electrode potential of each of them in the conditions of the experiment.

1. Two 250 ml beakers

2. Strip of zinc

3. Strip of copper

4. Two clamps to hold metal strips

5. Salt bridge filled with 3% agar and 1M KCL or KNO3

6. Voltmeter

Reagents:

1. 250 cm^3 of 1.0 M CuSO4

2. 250 cm^3 of !.0 M ZnSO4

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1. Pour one of the solutions into a beaker and the other solution into the other beaker.

2. Clamp the copper strip into the beaker containing the CuSO4 solution and do the equivalent with the zinc strip.

3. Connect the two beakers with the salt bridge. It is critical that the salt bridge reach beneath the surface of both solutions and that there are no air bubbles anywhere throughout the bridge.

4. Connect one lead from the voltmeter to each of the metal strips.

5. Record the reading on the voltmeter. You should get a reading near 1.10 V.

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