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Chemistry LibreTexts

Work From a Voltaic Cell

  • Page ID
    3101
  • [ "article:topic", "Fundamental" ]

     

    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.

    work.gif

    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= -2.37 V
    Cu 2+ (aq) + 2 e- ---> Cu (s) E= 0.34 V

    The reaction that has an overall positive cell potential is therefore

    Mg (s) ---> Mg 2+ (aq) + 2 e- E= 2.37 V
    2 H + (aq) + 2 e - ---> H2 (g) E=   0.00 V
    Mg (s) + 2 H + (aq) --->  Mg 2+ (aq) +   H2 (g) Eo cell  = 2.37 V

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

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