Work From a Voltaic Cell

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Chemical Concept Demonstrated

Electrochemical work with voltaic or galvanic cells

Demonstration

The beaker contains a solution of H₂SO₄.

A copper wire electrode along with a magnesium electrode are inserted into the solution.

The wires are connected to a flashbulb.

Alternately, a normal light bulb may be used.

Observations

The flashbulb is set off.

Explanation (including important chemical equations)

The standard-state reduction potentials are:

Mg ²⁺ (aq) + 2 e^- ---> Mg (s)	E^o= -2.37 V
Cu²⁺ (aq) + 2 e^- ---> Cu (s)	E^o= 0.34 V

The reaction that has an overall positive cell potential is therefore

Mg (s) ---> Mg ²⁺ (aq) + 2 e^-	E^o= 2.37 V
2 H⁺ (aq) + 2 e^- ---> H₂ (g)	E^o= 0.00 V
Mg (s) + 2 H⁺ (aq) ---> Mg ²⁺ (aq) + H₂ (g)	E^o_cell = 2.37 V

Electrons flow from the magnesium electrode to the copper electrode through the external circuit, setting off the flashbulb.

Contributors

Dr. George Bodner (Purdue University)

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