A galvanic cell converts chemical energy into electrical energy using a spontaneous redox reaction. Two half-cells keep oxidation and reduction separated, so electrons must travel through an external wire. The salt bridge completes the circuit by allowing ions to move between solutions without mixing them completely.
Understanding this structure helps students connect particle motion, voltage, and chemical change in one clear model.
Cell notation is a compact way to describe the same cell diagram in symbols. It lists the anode on the left, the cathode on the right, and uses vertical lines to show phase boundaries. The salt bridge is represented by a double vertical line, which marks the separation between the two half-cells.
Reading cell notation correctly lets you identify where oxidation occurs, where reduction occurs, and which direction electrons and ions move.
Key Facts
- Oxidation occurs at the anode, and reduction occurs at the cathode.
- Electrons flow through the wire from anode to cathode in a galvanic cell.
- Cell notation order is anode | anode solution || cathode solution | cathode.
- A single vertical line, |, represents a phase boundary, and a double vertical line, ||, represents the salt bridge.
- Standard cell potential is E°cell = E°cathode - E°anode.
- For Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s), the overall reaction is Zn(s) + Cu2+(aq) -> Zn2+(aq) + Cu(s).
Vocabulary
- Salt bridge
- A connection containing mobile ions that maintains charge balance between half-cells while completing the circuit.
- Anode
- The electrode where oxidation occurs and electrons are produced.
- Cathode
- The electrode where reduction occurs and electrons are consumed.
- Cell notation
- A shorthand symbolic form that shows the substances, phases, and half-cell arrangement of an electrochemical cell.
- Half-cell
- One side of an electrochemical cell containing an electrode and the solution involved in either oxidation or reduction.
Common Mistakes to Avoid
- Putting the cathode on the left in cell notation is wrong because galvanic cell notation is written with the anode on the left and the cathode on the right.
- Saying electrons flow through the salt bridge is wrong because electrons move through the external wire while ions move through the salt bridge.
- Forgetting ion migration is wrong because charge would build up in each half-cell and stop the redox reaction if ions could not move.
- Using E°cell = E°anode - E°cathode is wrong because standard cell potential is calculated as E°cell = E°cathode - E°anode.
Practice Questions
- 1 A cell is written as Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s). Identify the anode, cathode, direction of electron flow, and overall reaction.
- 2 Using E°red(Cu2+/Cu) = +0.34 V and E°red(Zn2+/Zn) = -0.76 V, calculate E°cell for Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s).
- 3 A galvanic cell has E°cathode = +0.80 V and E°anode = +0.34 V. Calculate E°cell and state whether the cell is spontaneous under standard conditions.
- 4 Explain why a galvanic cell stops producing current if the salt bridge is removed, even though the electrodes and solutions are still present.