Lecture Room Volt Meter
Procedure
- Cut wedges out of a piece of 9cm filter paper so that three equal spokes ~1cm wide are left (should look like a 'Y'). Cut the tips off so the 'Y' fits into the dispo petri dish. .
- Place 2-3 drops 1M CuSO4 at one end of the 'Y', repeat with 1M ZnSO4, and 1M Pb(NO3)2. The solutions will start to wick along the paper. Before they merge add 1-2 drops 1M Na2SO4 (salt bridge) to the center of the 'Y' to stop the wicking. .
- Position 1cm2 pieces of Zn, Cu, and Pb over their salts at the tips of the 'Y'. .
- With the meter set on center zero, measure the voltage. Switching leads shows direction of electron flow. Be sure the 3V module is in place.
| Reactions | E (volts) |
| Cu2+ + 2e- --> Cu (s) | 0.337 |
| Pb2+ + 2e- --> Pb (s) | -0.126 |
| Zn2+ + 2e- --> Zn (s) | -0.7628 |
| Lead | Voltage Observed | ||||
|---|---|---|---|---|---|
| (-) | (+) | Lecture Meter | Fluka Meter | Literature* | |
| Zn | Cu | 1.1 | 1.091 | 1.0998 | |
| PB | 0.6 | 0.599 | 0.6368 | ||
| Pb | Zn | 0.6 | 0.599 | 0.6368 | |
| Cu | -0.5 | -0.488 | -0.463 | ||
| Cu | Zn | -1.1 | -1.091 | -1.0998 | |
| Pb | -0.5 | -0.488 | -0.463 |
*Quantitative Chemistry, Jurg Waser