Skip to content

The atomic mass of… (Class 12 Physics SQP 2026-27, Q24)

questionbuddy.in/q/cbse-12-physics-2026-27-sqp-q24-atomic-mass-calculate-binding-energy

PhysicsCBSE Class 12 · Sample paper, session 2026-27 · 3 marks · Short answer

CBSE Class 12 Physics sample paper 2026-27: question 24

From the official CBSE sample question paper for 2026-27, section C, question 24, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q24 · 3 marks · Short answerNuclei

The atomic mass of is 15.99493 u. Calculate the binding energy per nucleon of the oxygen nucleus.

(Given: mass of proton = 1.00727 u, mass of neutron = 1.00866 u, 1 u = 931.5 MeV/)

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

First count protons and neutrons in the nucleus.

Hint 2

Mass defect = (mass of separated nucleons) − (given mass).

Hint 3

Multiply the mass defect in u by 931.5 to get MeV, then divide by 16.

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. For O: , . Mass of nucleons: u.

    1 mark

  2. Mass defect: u.

    1 mark

  3. Binding energy: MeV. Binding energy per nucleon: MeV.

    1 mark

Answer: ≈ 7.71 MeV per nucleon (B ≈ 123.4 MeV)

Where the marks are

  • Total nucleon mass 16.12744 u (1 mark)
  • Mass defect 0.13251 u (1 mark)
  • B ≈ 123.4 MeV and B/A ≈ 7.71 MeV (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Nuclei, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: 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.