A galvanic cell uses the half-reactions Cu²⁺/Cu and Zn²⁺/Zn (E°_cell = +1.10 V). A student varies [Cu²⁺] while keeping [Zn²⁺] = 1.0 M.
These data are best explained by which trend?
- A
E is +1.10 V regardless of Q.
- B
E is independent of concentrations.
- C
E increases as [Cu²⁺] decreases.
- Dcheck_circle
E decreases as Q increases ([Cu²⁺] decreases pushes Q higher).
Explanation
Q = [Zn²⁺]/[Cu²⁺]. Lower [Cu²⁺] increases Q, and per Nernst equation E = E° − (0.0592/n)log Q, E drops as Q rises. Each ten-fold drop reduces E by ~0.030 V (n = 2), matching the data.