Investigating Metal Activity Differences

1. Obtain pennies that are minted after 1983 and cut them into half-sections using metal shears.  Note the silver-colored zinc core and the outer copper layer
2. Record the mass of two of the cut penny sections to the nearest 0.001 g.  Place them into a labeled 100 ml beaker.
3. Repeat step 2 with the other remaining half-section.
4. To each beaker, add about 20 mL of concentrated (12 M) hydrochloric acid.  When gas bubbles are no longer visible, the zinc has completely dissolved
5. Discard the acid in the sink once the bubbles have stopped appearing by filtering the copper particles still remaining.
6. Wash the remaining copper shells with distilled water.
7. When the copper shells have completely dried, weigh and record their masses.
8. Repeat steps 2-7 and instead add about 20 mL of concentrated SO4.

Procedure Sketches:

Safety:

• Avoid contact with hydrochloric acid, especially to the eyes as it can be extremely corrosive.
• Wear goggles at all times.
• Reactions should be carried out in a well-ventilated area.

Hypothesis:

Zns + 2HClaq → ZnCl2aq + H2g        spontaneous

        Cus + 2NO3- + 4H+ → Cu2+aq + 2NO2g + 2H2Ol

        Cus + 4 H+aq + SO42-aq → Cu2+aq + SO2g + 2H2Ol

        H3PO4 + 2H+ + Cu → H3PO3 + H2O + Cu2+

Data/Observations:

HCl:

1 M

3 M

6 M

SO4:

1 M

3 M

6 M

PO4:

1 M

3 M

6 M

Sample Calculations:

Original mass of penny section – Mass of Copper after reaction = mass of zinc in penny

      in penny section                       section

(mass of Zn in penny section) x 2 = mass of Zn in penny

(mass of Cu in penny section) x 2 = mass of Cu in penny

percent Cu in penny = mass of Cu      _        x 100

                                mass of penny

percent Zn in penny = mass of Zn      _        x 100

                                   mass of penny

E Calculations:

Zns + 2HClaq → ZnCl2aq + H2g

Zn → 2e- + Zn2+                        0.76 volts

2H+ + 2e- → H2                        0.00 volts

                                        0.76 volts

                                                spontaneous in HCl

Cu + 2H+ → H2 + Cu2+ 

Cu → Cu2+   + 2e-                        -0.34 volts

2H+ + 2e- → H2                          0.00 volts

                                                -0.34 volts

not spontaneous in HCl

3Cu + 8H+ + 2NO3- → 3Cu2+ + 2NO + 4H2O

NO3- + 4H+ + 3e- → NO + 2H2O        0.96 volts

Cu → Cu2+   + 2e-                                 -0.34 volts

                                           0.62 volts

spontaneous in HNO3

3Zn + 8H+ + 2NO3- → 3Zn2+ + 2NO + 4H2O

NO3- + 4H+ + 3e- → NO + 2H2O        0.96 volts

Zn → Zn2+ + 2e-                                   0.76 volts

1.72 volts

spontaneous in HNO3

Cu + 2H+ → H2 + Cu2+   

Cu → Cu2+  + 2e-                        -0.34 volts

2H+ + 2e- → H2                                  0.00 volts

- 0.34 volts

                                                not spontaneous in H2SO4

Zn + 2H+ → Zn2+ + H2

        Zn → 2e- + Zn2+                        0.76 volts

2H+ + 2e- → H2                        0.00 volts

                                        0.76 volts

                                                spontaneous in H2SO4

H3PO4 + 2H+ + Cu → H3PO3 + H2O + Cu2+

H3PO4 + 2H+ + 2e- → H3PO3 + H2O        

Cu → Cu2+ + 2e-                        

Work Cited:

http://www.pkwy.k12.mo.us/west/teachers/anderson/pack5/labpenny.pdf