Write the Nernst equation for the Daniell cell, and use it to calculate the EMF of Zn(s) | Zn²⁺(0.1 M) || Cu²⁺(0.01 M) | Cu(s) at 298 K. (E°cell = 1.10 V)

1. 1 · State the principle in one line. The Nernst equation gives the potential of a cell at any concentration: E_cell = E°cell − (2.303RT/nF) log Q.
2. 2 · Write the cell reaction. Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), so n = 2 electrons.
3. 3 · Write the Nernst equation. E_cell = E°cell − (0.059/2) log ([Zn²⁺]/[Cu²⁺]) at 298 K.
4. 4 · Substitute. E_cell = 1.10 − 0.0295 × log (0.1/0.01) = 1.10 − 0.0295 × log 10.
5. 5 · Calculate and box the answer. E_cell = 1.10 − 0.0295 = 1.0705 V ≈ 1.07 V.
6. 6 · Interpret. The EMF is below 1.10 V because the product ion, Zn²⁺, is more concentrated than the reactant ion, Cu²⁺.

Scoring tip: Write Q as products over reactants and leave out the solid metals. State n before you substitute.