Name: _____________________________

Date: _____________________________

In this lab, we will determine the percent composition of a modern (post-1982) penny by using a strong

acid to react and dissolve the zinc core, leaving only the copper coating. Once only copper remains,

we will compare its mass to the entire mass of the penny to determine how much of a penny is copper

and how much is zinc.

penny (1983 or later)

3 M hydrochloric acid (HCl), 50 mL

metal file

beaker

gloves

1. Obtain a clean post-1982 penny.

2. Measure and record the mass of the penny.

3. Using a metal file, file three, oppositely-placed small grooves into the edge of the penny. The

grooves must be deep enough so that the zinc is exposed, but not so deep that the penny's mass

is greatly affected.

4. Obtain a small beaker and label it with your name.

5. While wearing gloves, carefully pour 50mL 3M HCl into a small beaker.

6. Carefully place the penny in the acid. Observe the effect the acid has on the copper outside of

the penny.

7. Place your labeled beaker under either fume hood to react overnight.

8. After the penny has fully reacted, carefully pour some water from another beaker into the acid to

dilute it.

9. Carefully remove the remainder of the penny with a pair of tongs.

10. Gently rinse the penny in the sink and pat it dry with paper towels.

11. Put the penny in a small beaker and place it in the oven for 5-10 minutes to allow it to dry

completely.

12. Dispose of the acid in the large waste beaker in the fume hood (DO NOT POUR IT DOWN THE

SINK).

13. Remove the penny and measure and record its new mass.

14. Dispose of the penny and clean all used glassware.

(copper + zinc)

(copper only)