Galvanic Cell & Daniell Cell | Electrochemistry Class 12 Notes

Galvanic (Voltaic) Cell

Electrochemistry Class 12 | Principles, Daniell Cell & IUPAC Notation

1. What is a Galvanic Cell?

A Galvanic cell (or Voltaic cell) is an electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy. The classic example is the Daniell Cell.

2. Working of the Daniell Cell

The Daniell cell consists of a Zinc rod dipped in $ZnSO_4$ solution and a Copper rod dipped in $CuSO_4$ solution, connected by a Salt Bridge.

Overall Redox Reaction: $$ Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s) $$

Electrode Reactions

• At Anode (Oxidation): Zinc loses electrons.
  $Zn(s) \rightarrow Zn^{2+}(aq) + 2e^-$
• At Cathode (Reduction): Copper ions gain electrons.
  $Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$

3. Polarity & Electron Flow

Unlike electrolytic cells, the polarity in Galvanic cells is:

• Anode: Negative (-) Terminal (Source of electrons)
• Cathode: Positive (+) Terminal (Sinks electrons)

Remember "LOAN": Left - Oxidation - Anode - Negative

Direction of Flow: Electrons flow from Anode to Cathode in the external circuit. Current flows from Cathode to Anode.

4. Functions of Salt Bridge

An inverted U-tube containing inert electrolyte (like $KNO_3$, $KCl$) in agar-agar jelly.

1. It completes the internal circuit.
2. It maintains electrical neutrality of the two half-cell solutions.
3. It minimizes Liquid Junction Potential.

5. IUPAC Cell Representation

A cell is represented as: Anode || Cathode

$$ Zn(s) | Zn^{2+}(aq) \parallel Cu^{2+}(aq) | Cu(s) $$

Cell EMF Calculation:

$$ E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} $$ $$ E^\circ_{cell} = E^\circ_{Right} - E^\circ_{Left} $$

Test Your Concepts

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