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What type of battery is… (Class 12 Chemistry 2026, Q23b)

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ChemistryCBSE Class 12 · Board exam 2026, set 56/1/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2026: question 23(b)

Set in the CBSE Class 12 board exam of 2026, paper 56/1/1, section C, question 23(b), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q23(b) · 3 marks · Short answerElectrochemistry

What type of battery is Mercury cell ? Why it is more advantageous than dry cell ? Write overall reaction taking place in Mercury cell.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 56/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Can a mercury cell be recharged?

Hint 2

Do any ions appear in the overall cell reaction? How does that affect the voltage?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. The mercury cell is a primary cell (it cannot be recharged).

    1 mark

  2. Advantage over the dry cell: it gives a constant potential of about 1.35 V throughout its life, because the overall reaction involves no ions whose concentration changes. A dry cell's voltage falls as it is used. This makes the mercury cell suitable for hearing aids and watches.

    1 mark

  3. Overall reaction:

    1 mark

Answer: A primary cell; it gives a constant voltage (~1.35 V); Zn(Hg) + HgO(s) → ZnO(s) + Hg(l)

Where the marks are

  • Primary cell (1 mark)
  • Constant potential throughout its life (1 mark)
  • Correct overall reaction (1 mark)

Revise the chapter

  • Chapter: Electrochemistry (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Electrochemistry, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 56/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.