What NEET Asks
- Questions on identifying anode/cathode, oxidation/reduction half-reactions.
- Cell notation representation is frequently tested.
- Understanding the role of the salt bridge is crucial for 4 marks questions.
- Typically 1-2 questions from Electrochemistry, often covering basic cell components.
Key Points
- Daniel Cell: A type of galvanic (voltaic) cell where chemical energy converts to electrical energy spontaneously.
- Components: Zinc electrode in ZnSO₄ solution (anode), Copper electrode in CuSO₄ solution (cathode), connected by a salt bridge.
- Anode (Negative): Oxidation occurs: Zn(s) → Zn²⁺(aq) + 2e⁻. Its mass decreases.
- Cathode (Positive): Reduction occurs: Cu²⁺(aq) + 2e⁻ → Cu(s). Its mass increases.
- Electron Flow: From anode (Zn) to cathode (Cu) through the external circuit.
- Salt Bridge: Maintains electrical neutrality by allowing ion migration, prevents charge build-up, and completes the circuit.
Must-Know Formula / Reaction
Anode (Oxidation): Zn(s) → Zn²⁺(aq) + 2e⁻ Cathode (Reduction): Cu²⁺(aq) + 2e⁻ → Cu(s) Overall Cell Reaction: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) Cell Notation: Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s)
|: Represents a phase boundary (electrode | electrolyte).||: Represents the salt bridge.- Left side: Anode (site of oxidation), Right side: Cathode (site of reduction).
Common Mistakes
- Students often confuse the anode and cathode, or oxidation and reduction sites. Remember "AN OX, RED CAT" for Anode Oxidation and Reduction Cathode.
- Don't forget the salt bridge's critical role; without it, the cell stops working quickly due to charge accumulation.
- Incorrectly writing cell notation (e.g., switching anode/cathode, or omitting state symbols).
Rapid Revision
The Daniel Cell utilizes Zn (anode, oxidation) and Cu (cathode, reduction) to produce electricity. Electrons move from Zn to Cu. The salt bridge ensures charge neutrality. Cell notation: Zn|Zn²⁺||Cu²⁺|Cu.