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FOLLOW THE SIGNAL
What can a voltage reveal about a chemical cell?
A voltmeter reads the difference between the copper and zinc terminals. Its sensing path should draw negligible current. In potentiometric work, a sensing electrode is often compared with a reference electrode; the reported value therefore needs its reference. Following potential over time can reveal drift. An open-circuit trace is a measurement of potential, not a measurement of reaction rate.
MAKE THE CONNECTION
Increase both activities tenfold within bounds. What changes?
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CHANGE A CONDITION · COMPARE THE RESPONSE
| log₁₀[a(Zn²⁺) / a(Cu²⁺)] | Current |
|---|---|
| -3.00 | 1.19 |
| -2.00 | 1.16 |
| -1.00 | 1.13 |
| 0.00 | 1.10 |
| 1.00 | 1.07 |
| 2.00 | 1.04 |
| 3.00 | 1.01 |
25 °C; E° ≈ 1.10 V; dimensionless ion activities, pure solids and locally equilibrated interfaces. Junction potential and load effects omitted.