The half-cell reactions in an ordinary dry cell (Leclanché cell) are as follows:

Anode (Negative Electrode):

* Oxidation: Zn(s) → Zn²⁺(aq) + 2e⁻

Cathode (Positive Electrode):

* Reduction: 2MnO₂(s) + 2H⁺(aq) + 2e⁻ → Mn₂O₃(s) + H₂O(l)

Overall Reaction:

Zn(s) + 2MnO₂(s) + 2H⁺(aq) → Zn²⁺(aq) + Mn₂O₃(s) + H₂O(l)

Explanation:

* Anode (Zinc): The zinc electrode is oxidized, meaning it loses electrons and forms zinc ions (Zn²⁺). These electrons flow through the external circuit to the cathode.

* Cathode (Manganese Dioxide): The manganese dioxide (MnO₂) is reduced, meaning it gains electrons. The electrons react with MnO₂, water, and hydrogen ions (H⁺) to form manganese(III) oxide (Mn₂O₃) and water. The hydrogen ions come from the ammonium chloride (NH₄Cl) electrolyte.

Note:

* The dry cell is not truly "dry" as it contains a moist paste electrolyte.

* The electrolyte is a mixture of ammonium chloride (NH₄Cl) and zinc chloride (ZnCl₂).

* The reaction is not fully reversible, making the dry cell a primary cell (non-rechargeable).