Floating Pennies
Removal of Zinc from Pennies
Objective: The different reactivities of copper and zinc to hydrochloric acid will be used to separate the two metals in a post-1983 penny. The percent of zinc and of copper can be calculated as well as the economic value of each.
Time: This activity must be performed over a period of two days. Only a few minutes of student time are required each day.
Materials and Supplies:
one penny (newer than 1983)
20 ml 6 M HCl
100 ml beaker
triangular file
centigram balance
forceps or tongs
acetone (optional)
General Safety Guidelines:
Procedure:
Questions and Calculations:
1. From the masses of the penny before and after the reaction, calculate the mass of zinc in the penny.
2. Calculate the percentage of zinc and the percentage of copper in the penny.
3. From a newspaper look up the prices of copper and zinc at the present time. Note the units. If the units are dollars per ounce, convert the value to dollars per gram. (1 pound = 454 grams)
4. From the mass of zinc and the current market value of zinc, calculate the value of zinc in the penny. Do the same for the copper in the penny.
5. Determine the value of the copper in the pre-1982 penny.
Why do you think our government switched to a copper-clad zinc penny?