Key Fact
Common batteries
Dry cell (Leclanché): Zn anode, MnO₂/C cathode, ~1.5 V. Lead accumulator: Pb anode, PbO₂ cathode, H₂SO₄ electrolyte, ~2 V/cell. Fuel cell: H₂/O₂ → H₂O + electrical energy.
-- NCERT Class 12 Chemistry, Ch. 2, p. 54Dry Cell Lead Accumulator
8 MCQs9-step worked example
Source: NCERT Redox Reactions and ElectrochemistryOfficial key: NTA-verifiedLast updated: 24 Sep 2026
Dry Cell Lead Accumulator, explained for NEET
The dry cell (Leclanché cell) and the lead-acid accumulator are two commercially important electrochemical cells that NEET tests at the recall and direct-application level. The topic appears with low-to-medium frequency (~0.4 questions/year), but when it appears, marks are easy to secure — or easy to lose if you confuse the electrode reactions.
Dry cell (Leclanché cell). The anode is zinc (the outer casing). The cathode is a carbon rod surrounded by powdered MnO₂ and carbon black. The electrolyte is a moist paste of NH₄Cl and ZnCl₂. At the anode: Zn → Zn²⁺ + 2e⁻. At the cathode: MnO₂ + NH₄⁺ + e⁻ → MnO(OH) + NH₃. The cell potential is approximately 1.5 V. It is a primary cell — non-rechargeable — because the zinc casing is irreversibly consumed (NCERT Class 12 Chemistry Chapter 2, page 54).
Lead-acid accumulator. The anode is spongy lead (Pb). The cathode is PbO₂ packed on a lead grid. The electrolyte is ~38% H₂SO₄. During discharge: at the anode, Pb → PbSO₄; at the cathode, PbO₂ → PbSO₄. Both electrodes convert to lead sulfate — this is the key detail NEET exploits. The cell potential is approximately 2 V per cell (six cells give the familiar 12 V car battery). It is a secondary cell — rechargeable — because the electrode reactions reverse on applying external voltage.
Common confusion NEET targets: mixing up which cell is primary vs. secondary; confusing the anode material (zinc in dry cell, lead in accumulator); forgetting that both electrodes in the lead accumulator form PbSO₄ during discharge; and misidentifying the electrolyte (paste in dry cell, dilute H₂SO₄ in accumulator).
Can you answer these Dry Cell Lead Accumulator MCQs?
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
MCQ 1Easy RecallPractice
In a Leclanché dry cell, the anode is made of:
Show answer and why every option is right or wrong
Answer: D. The zinc casing acts as the anode in a dry cell. The carbon rod is the current collector at the cathode side (NCERT Class 12 Chemistry Chapter 2, page 54).
Why A is wrong: A — The carbon rod serves as the cathode current collector, not the anode. This is a frequent swap error.
Why B is wrong: B — MnO₂ is the depolarizer packed around the cathode carbon rod, not the anode.
Why C is wrong: C — Lead is the anode material in a lead-acid accumulator, not in a dry cell.
MCQ 2Easy RecallPractice
The lead-acid accumulator is classified as a:
Show answer and why every option is right or wrong
Answer: A. A lead-acid accumulator is rechargeable — its electrode reactions are reversible upon applying external voltage — making it a secondary cell (NCERT Class 12 Chemistry Chapter 2, page 54).
Why B is wrong: B — A fuel cell continuously consumes fuel (e.g., H₂-O₂ cell). The accumulator stores chemical energy internally.
Why C is wrong: C — A primary cell is non-rechargeable (e.g., the dry cell). The lead accumulator can be recharged by reversing the discharge reactions.
Why D is wrong: D — A concentration cell has identical electrodes differing only in electrolyte concentration. The lead accumulator has two different electrode materials (Pb and PbO₂).
MCQ 3Easy RecallPractice
The electrolyte used in a dry cell is:
Show answer and why every option is right or wrong
Answer: B. The Leclanché dry cell uses a moist paste of ammonium chloride and zinc chloride as the electrolyte (NCERT Class 12 Chemistry Chapter 2, page 54).
Why A is wrong: A — Dilute H₂SO₄ is the electrolyte of the lead-acid accumulator, not the dry cell.
Why C is wrong: C — Concentrated HCl is not used in any standard commercial cell discussed in the NCERT syllabus.
Why D is wrong: D — Aqueous KOH is used in alkaline batteries and certain fuel cells, not in the standard Leclanché dry cell.
MCQ 4Direct ApplicationPractice
During discharge of a lead-acid accumulator, the product formed at BOTH electrodes is:
Show answer and why every option is right or wrong
Answer: C. During discharge, Pb at the anode is oxidized to PbSO₄ and PbO₂ at the cathode is reduced to PbSO₄. Both electrodes convert to lead sulfate (NCERT Class 12 Chemistry Chapter 2, page 54).
Why A is wrong: A — Spongy Pb is the anode material BEFORE discharge. During discharge it is consumed, not formed.
Why B is wrong: B — PbO is not a product in either the discharge or charge half-reactions of the lead-acid cell.
Why D is wrong: D — PbO₂ is the cathode material before discharge. It is consumed during discharge, not formed.
MCQ 5Direct ApplicationPractice
A standard car battery is rated at 12 V. If each lead-acid cell produces approximately 2 V, the number of cells connected in series is:
Show answer and why every option is right or wrong
Answer: C. Number of cells = total voltage / voltage per cell = 12 V / 2 V = 6. Six cells are connected in series in a standard 12 V lead-acid battery.
Why A is wrong: A — 3 cells × 2 V = 6 V, not 12 V. This error halves the cell count.
Why B is wrong: B — 4 cells × 2 V = 8 V. This does not match the 12 V rating.
Why D is wrong: D — This would give 12 × 2 V = 24 V, which is a heavy-duty truck battery, not a standard car battery.
MCQ 6Direct ApplicationPractice
During the charging of a lead-acid accumulator, the reaction at the cathode (negative plate) is:
Show answer and why every option is right or wrong
Answer: B. During charging, the reaction reverses. At the negative plate (cathode during charging), PbSO₄ is reduced back to spongy Pb: PbSO₄ + 2e⁻ → Pb + SO₄²⁻ (NCERT Class 12 Chemistry Chapter 2, page 54).
Why A is wrong: A — This is a generic oxidation half-reaction, not the specific charging cathode reaction. During charging, reduction occurs at the cathode.
Why C is wrong: C — This is the reaction at the positive plate (anode) during charging, where PbSO₄ is oxidized back to PbO₂. This is the opposite electrode.
Why D is wrong: D — This is the cathode reaction during DISCHARGE, not during charging. Charging reverses the discharge reactions.
MCQ 7Concept TrapPractice
Which of the following correctly distinguishes a dry cell from a lead-acid accumulator?
Show answer and why every option is right or wrong
Answer: A. The dry cell operates at ~1.5 V and is a primary (non-rechargeable) cell, while each cell in the lead-acid accumulator operates at ~2 V and is secondary (rechargeable). The voltage distinction is a direct factual comparison (NCERT Class 12 Chemistry Chapter 2, page 54).
Why B is wrong: B — This swaps the electrolytes. The dry cell uses NH₄Cl/ZnCl₂ paste; the lead accumulator uses dilute H₂SO₄.
Why C is wrong: C — This reverses the classification. The dry cell is primary (non-rechargeable) and the lead accumulator is secondary (rechargeable).
Why D is wrong: D — The lead-acid accumulator is rechargeable (secondary). Only the dry cell is non-rechargeable (primary).
MCQ 8Concept TrapPractice
When a lead-acid accumulator is fully discharged, the density of the H₂SO₄ electrolyte decreases. The best explanation is:
Show answer and why every option is right or wrong
Answer: D. The overall discharge reaction consumes H₂SO₄ and produces water (Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O). As sulfuric acid is consumed and water is formed, the electrolyte becomes more dilute and its density drops. This density change is used practically to test the state of charge.
Why A is wrong: A — Evaporation would increase acid concentration and density, not decrease it. The opposite is observed during discharge.
Why B is wrong: B — SO₄²⁻ ions are incorporated into solid PbSO₄ on the electrode plates, not removed from the cell. The net effect is H₂SO₄ depletion from the electrolyte.
Why C is wrong: C — Lead does not dissolve freely in the acid. Lead converts to PbSO₄ at the electrode surface; it is the consumption of H₂SO₄ that drives the density decrease.
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How do you solve a Dry Cell Lead Accumulator question? A worked example
- 1
Given
A lead-acid accumulator consists of cells, each with spongy Pb as anode and PbO₂ as cathode, with ~38% H₂SO₄ electrolyte. Each cell produces approximately 2 V. A battery is rated at 12 V.
- 2
Required
(a) Number of cells in the battery.
(b) Write the overall discharge reaction.
(c) Explain why electrolyte density decreases during discharge. - 3
Concept
The lead-acid accumulator is a secondary cell. During discharge, both electrodes form PbSO₄ and H₂SO₄ is consumed with water produced. Cells are connected in series so total voltage = n × voltage per cell.
- 4
Formula
Total voltage = number of cells × voltage per cell.
Overall discharge: Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l) - 5
Substitution
12 V = n × 2 V
- 6
Calculation
n = 12 / 2 = 6 cells.
Note: 12 and 2 are exact integers (specified values), so no significant-figure ambiguity arises. - 7
Final answer
(a) 6 cells connected in series.
(b) Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l).
(c) H₂SO₄ is consumed and H₂O is produced during discharge, diluting the electrolyte and reducing its density. This is why a hydrometer reading can indicate charge level. - 8
Common trap
Forgetting that BOTH electrodes form PbSO₄ during discharge. Students sometimes write Pb at the cathode product or PbO₂ at the anode product. The symmetry of the PbSO₄ product is the single most tested detail.
- 9
Similar NEET-style question
"A lead-acid battery rated at 24 V is used in a heavy vehicle. How many cells does it contain, and what is the product at both electrodes during discharge?"
Answer: 12 cells (24 V / 2 V); product at both electrodes is PbSO₄.
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What to remember before solving Dry Cell Lead Accumulator questions
More in Redox Reactions and Electrochemistry: 4 exam traps and mistakes · 5 formulas · 2 question patterns from its other lessons.
Dry Cell Lead Accumulator questions from past NEET papers
No question in our NEET 2020–2025 set targets this topic directly.
All 21 past-paper questions from Redox Reactions and Electrochemistry →
Sources
NCERT refs: Class 12 Chemistry Chapter 2, p.54
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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