Which of the following is used as a depolarizer in a Denial cell?

Analyze the question: "Denial cell" is a misspelling of Daniell cell. The question asks which substance acts as the depolarizer in it.

Concept: Polarization in a simple cell happens when hydrogen gas bubbles form on the positive electrode (copper). The bubbles insulate the electrode and raise the internal resistance, so the cell's current drops. A depolarizer is a substance that removes the hydrogen, usually by oxidizing it, so the cell keeps working.

Solution: The Daniell cell has:

• A zinc rod in dilute tetraoxosulphate(VI) acid (H₂SO₄) or zinc sulphate, inside a porous pot
• A copper rod in copper(II) tetraoxosulphate(VI) solution (CuSO₄)

At the copper electrode, the Cu²⁺ ions are discharged instead of H⁺ ions:

Cu²⁺ + 2e⁻ → Cu

Hydrogen therefore never forms on the copper plate. The CuSO₄ solution is the depolarizer.

Checking the other options:

• A. Ammonium chloride is the electrolyte in the Leclanché cell, not a depolarizer.
• C. Manganese(IV) oxide is the depolarizer in the Leclanché cell, a common trap. It is not used in the Daniell cell.
• D. Tetraoxosulphate(VI) acid is the electrolyte around the zinc (or in a simple cell), not the depolarizer.
• E. Water is just a solvent.

**Answer: B. Copper(II) tetraoxosulphate(VI) solution.

Exam tip: Remember the pairs:

• Daniell cell → CuSO₄
• Leclanché cell → MnO₂

If the question says "Daniell", think copper sulphate. If it says "Leclanché" or "dry cell", think manganese(IV) oxide.