A high school girl was getting ready for a big date but discovered with horror that her silver necklace was tarnished. Having just studied about redox reactions and electrochemical cells in chemistry class, she grabbed some aluminum foil, put it in a dish, and placed her necklace on top of the foil. Then she added some baking soda, a little salt, and hot water. Within a few minutes, her necklace was bright and shiny again.
The formula for silver tarnish is Ag2S. Use the balanced equation to answer the following questions:
3Ag2S + 2Al(s) Al2S3 + 6Ag(s)
a. What makes this an oxidation-reduction reaction?
b. Write the half-reactions showing the oxidation and reduction reactions. Identify which is the oxidation reaction and which is the reduction reaction.
c. What is oxidized in the reaction? What is reduced?
d. In this simple electrochemical cell, what functions as the anode? What is the cathode?
e. Is this a galvanic cell or electrolytic cell? Explain your answer.
f. What would the overall potential for this cell be?