What NEET Asks
- Identify and differentiate between galvanic and electrolytic cells based on energy conversion, spontaneity, and electrode polarity.
- Predict the nature of reactions (oxidation/reduction) at specific electrodes.
- Questions often involve scenario-based identification or direct comparison of properties.
Key Points
- Galvanic (Voltaic) Cell: Converts chemical energy (from spontaneous redox) into electrical energy. ΔG < 0.
- Electrolytic Cell: Converts electrical energy into chemical energy (drives non-spontaneous redox). Requires external power. ΔG > 0.
- Anode: Site of oxidation in both cells. In galvanic, it's the negative electrode. In electrolytic, it's the positive electrode.
- Cathode: Site of reduction in both cells. In galvanic, it's the positive electrode. In electrolytic, it's the negative electrode.
- Electron Flow: Always from anode to cathode via the external circuit.
- Salt Bridge: Essential for galvanic cells to maintain charge neutrality; generally absent in simple electrolytic cells.
Must-Know Formula / Reaction
- Spontaneity Criterion: For Galvanic Cells, ΔG < 0 (spontaneous reaction). For Electrolytic Cells, ΔG > 0 (non-spontaneous reaction, requires energy input).
Common Mistakes
- Students often confuse the polarity of anode and cathode between galvanic and electrolytic cells. Remember: Oxidation at Anode, Reduction at Cathode is constant, but polarity changes.
- Don't confuse the direction of energy conversion: Chemical → Electrical (Galvanic) vs. Electrical → Chemical (Electrolytic).
- Forgetting the role of the salt bridge in maintaining electrical neutrality in galvanic cells.
Rapid Revision
- Galvanic: Chemical→Electrical, Spontaneous, Anode(-), Cathode(+).
- Electrolytic: Electrical→Chemical, Non-spontaneous, Anode(+), Cathode(-).
- Oxidation always at Anode, Reduction always at Cathode.