Lecture Room Volt Meter with Bologna for a Salt Bridge
Procedure
- Pour 0.1M CuSO4 into one 400mL beaker and 0.1M ZnSO4 into another up to about the 300mL mark.
- Place a copper strip into the CuSO4 solution and a zinc strip into the ZnSO4 solution. Hook up double alligator clip leads from the zinc and copper strips to the leads on the lecture size volt meter. It should read zero volts.
- Hang a piece of filter paper soaked in saturated Na2SO4 over the ends of the beakers to form a salt bridge between the solutions
- 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.
- Hang a slice of bologna over the ends of the beakers, being sure that the bologna is immersed in both the CuSO4 and ZnSO4 solutions and measure the voltage. Hot dogs would work as well but they break when one tries to bend them over two beakers.
| Reactions | E (volts) |
| Cu2+ + 2e- --> Cu (s) | 0.337 |
| Zn2+ + 2e- --> Zn (s) | -0.7628 |
| Lead | Voltage Observed | ||||
|---|---|---|---|---|---|
| (-) | (+) | Lecture Meter | Fluka Meter | Literature* | |
| Zn | Cu | 1.1 | 1.091 | 1.0998 | |
| Cu | Zn | -1.1 | -1.091 | -1.0998 |
*Quantitative Chemistry, Jurg Waser