Chapter 16 · Oxidation and Reduction
16.6Batteries: Using Chemistry to Generate Electricity
11 min · two checks
Predict
In a galvanic cell, which electrode is the anode?
The idea
- Label anode, cathode, and electron flow.
- Describe a salt bridge’s job.
A galvanic (voltaic) cell separates the two half-reactions. Oxidation is at the anode. Reduction is at the cathode. Electrons flow from anode to cathode through the wire. Ions flow through a salt bridge or porous barrier to keep the solutions electrically neutral; without that bridge the current stops almost immediately as charge builds up. In a discharging battery the anode is labeled negative because electrons come out of it into the circuit.
A dry cell, a lead-acid car battery, and a fuel cell are all this pattern with different chemicals. A lead-acid cell uses Pb and PbO₂ in sulfuric acid and can be recharged, which forces the reactions backward with an external voltage. A fuel cell is a galvanic cell whose reactants, such as H₂ and O₂, are supplied continuously instead of being sealed inside. Recharge is electrolysis, the next section, applied on purpose.
Keep these
- Anode: oxidation. Cathode: reduction.
- Electrons flow anode → wire → cathode.
- A salt bridge lets ions move so charge does not pile up.