Question

Some statements about Leclanche ll are:
Anode is zinc metal
Cathode is graphite rod surrounded by powdered {MnO2} and carbon
Electrolyte is a moist paste of ZnO and KOH
Oxidation product is ZnO

• A. only statements I and II are correct.
• B. only statements I is correct.
• C. only statements  II is correct.
• D. None of them are correct.

Hint:

Key Facts about Leclanché Cell:

• Anode: Zinc container, undergoes oxidation.
• Cathode: Graphite rod surrounded by MnO2 and carbon powder.
• Electrolyte: Moist paste of NH4Cl and ZnCl2.
• Overall reaction: \[ Zn + 2MnO2 + 2NH4Cl -> ZnCl2 + Mn2O3 + 2NH3 + H2O \]
• Not rechargeable and commonly used in dry cells (e.g., torch batteries).

Answer 1

The Correct Option is A

The Leclanché cell is a type of primary battery (non-rechargeable) that operates via redox reactions between zinc and manganese dioxide.

• Statement I: Anode is zinc metal — Correct.
  Zinc metal acts as the anode and undergoes oxidation, releasing electrons:

\[ \mathrm{Zn} \rightarrow \mathrm{Zn^{2+}} + 2e^- \]

• Statement II: Cathode is graphite rod surrounded by powdered \( \mathrm{MnO_2} \) and carbon — Correct.
  The cathode consists of a graphite rod which acts as an inert conductor, embedded in a mixture of manganese dioxide and carbon powder. \( \mathrm{MnO_2} \) is reduced:

\[ \mathrm{MnO_2} + H^+ + e^- \rightarrow \mathrm{MnOOH} \]

• Statement III: Electrolyte is a moist paste of \( \mathrm{ZnO} \) and \( \mathrm{KOH} \) — Incorrect.
  This is not true for a Leclanché cell. The electrolyte in a Leclanché cell is actually a moist paste of ammonium chloride (\( \mathrm{NH_4Cl} \)) and zinc chloride (\( \mathrm{ZnCl_2} \)), not \( \mathrm{KOH} \).
• Statement IV: Oxidation product is \( \mathrm{ZnO} \) — Incorrect.
  In the Leclanché cell, the oxidation product is \( \mathrm{Zn^{2+}} \), typically forming \( \mathrm{ZnCl_2} \), not \( \mathrm{ZnO} \).

Hence, only statements I and II are correct.

Answer 2

Step 1: Understanding the components of Leclanché cell
The Leclanché cell is a primary battery commonly used in dry cell batteries.
- The anode is zinc metal, which acts as the negative electrode.
- The cathode consists of a graphite rod surrounded by a mixture of powdered manganese dioxide (MnO₂) and carbon, which acts as the positive electrode.

Step 2: Analyzing the electrolyte
In a typical Leclanché cell, the electrolyte is a moist paste of ammonium chloride (NH₄Cl) or zinc chloride (ZnCl₂), not zinc oxide (ZnO) and potassium hydroxide (KOH). The moist paste serves as the medium for ion conduction.

Step 3: Oxidation product
During the cell’s operation, zinc metal is oxidized to zinc ions (Zn²⁺), which generally combine with chloride ions to form zinc chloride, not zinc oxide (ZnO). Hence, the oxidation product is not ZnO.

Step 4: Conclusion
Only statements I (Anode is zinc metal) and II (Cathode is graphite rod surrounded by powdered MnO₂ and carbon) are correct. Statements III and IV are incorrect as the electrolyte and oxidation products mentioned do not correspond to the Leclanché cell.