Skip to main content
Chemistry LibreTexts

Work From a Voltaic Cell

 

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.

Contributors