Cell Operation: Daniell Cell Zn|$Zn^{2+}$||$Cu^{2+}$|Cu

[Zn Anode]
Zn(s) → $Zn^{2+}$(aq) + 2$e^{-}$
(oxidation; electrode dissolves)
        |
        | electrons flow through
        | external circuit
        ↓
[Cu Cathode]
$Cu^{2+}$(aq) + 2$e^{-}$ → Cu(s)
(reduction; electrode grows)

Ion flow in salt bridge (KCl in agar):

$Zn^{2+}$ accumulates (anode compartment) ← $K^{+}$ ions migrate in
$Cu^{2+}$ depleted (cathode compartment) ← $Cl^{-}$ ions migrate in
Purpose: Maintain electrical neutrality without mixing solutions

Electron path:

Zn(anode) → wire → voltmeter/bulb → Cu(cathode)

Overall cell reaction: $\text{Zn(s) + Cu}^{2+}\text{(aq)} \rightarrow \text{Zn}^{2+}\text{(aq) + Cu(s)}$

$E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = (+0.34) - (-0.76) = +1.10 \text{ V}$

Sign convention:

• Galvanic: Anode = negative (−); Cathode = positive (+)
• EMF is POSITIVE for spontaneous galvanic cells
• Electrons flow from anode (−) through external wire to cathode (+)
• Inside the cell: current flows from cathode to anode (conventional current)

Key points

• Cell notation: Anode | Anode-solution || Cathode-solution | Cathode
• Single vertical line (|) = phase boundary; double (||) = salt bridge
• Left = anode (oxidation); Right = cathode (reduction) — by IUPAC convention