Mass Defect & Binding Energy — MH-CET Physics MCQs with Solutions
Free MH-CET Physics Mass Defect & Binding Energy MCQs with step-by-step solutions (21 questions). Part of Structure of Atoms and Nuclei. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Mass Defect & Binding Energy · easy · theory
The mass defect of a nucleus is:
A. The difference between the sum of the masses of the free nucleons and the mass of the nucleus ✓ Correct
B. The difference between proton and neutron masses
C. The mass of the nucleus alone
D. The mass of the electrons in the atom
Solution: This missing mass has been converted into the binding energy that holds the nucleus together.
Q2 — Mass Defect & Binding Energy · easy · theory
The binding energy of a nucleus is related to its mass defect by:
A. $BE = \Delta m\,c$
B. $BE = \Delta m\,c^2$ ✓ Correct
C. $BE = \dfrac{\Delta m}{c^2}$
D. $BE = \dfrac{c^2}{\Delta m}$
Solution: It is the energy that would be needed to separate the nucleus completely into free nucleons.
Q3 — Mass Defect & Binding Energy · medium · theory
The binding energy per nucleon is greatest for nuclei of mass number around:
A. $120$
B. $56$ ✓ Correct
C. $4$
D. $238$
Solution: Iron-56 sits at the peak of the binding energy curve at about $8.8\text{ MeV}$ per nucleon.
Q4 — Mass Defect & Binding Energy · easy · theory
A nucleus with a higher binding energy per nucleon is:
A. More stable ✓ Correct
B. Less stable
C. Radioactive always
D. Larger in size
Solution: More energy per nucleon must be supplied to break it apart.
Q5 — Mass Defect & Binding Energy · medium · theory
Energy is released in nuclear fusion of light nuclei because:
A. Mass is created in the process
B. The product has a lower binding energy per nucleon
C. The Coulomb barrier disappears
D. The product has a higher binding energy per nucleon than the reactants ✓ Correct
Solution: Moving up the binding energy curve towards iron always liberates energy.
Q6 — Mass Defect & Binding Energy · medium · theory
Energy is released in the fission of heavy nuclei because:
A. The parent nucleus has zero binding energy
B. The fragments are larger than the parent
C. Neutrons are destroyed in the process
D. The fragments have a higher binding energy per nucleon than the parent ✓ Correct
Solution: Splitting a very heavy nucleus also moves the system towards the peak of the curve.
Q7 — Mass Defect & Binding Energy · medium · theory
The nuclear force between nucleons is:
A. Effective only between protons
B. Weaker than the gravitational force
C. Short ranged, charge independent and much stronger than the Coulomb force ✓ Correct
D. Long ranged and charge dependent
Solution: It acts over about $10^{-15}\text{ m}$ and binds protons and neutrons equally.
Q8 — Mass Defect & Binding Energy · medium · theory
The energy released in the fission of a single uranium-235 nucleus is approximately:
A. $200\text{ MeV}$ ✓ Correct
B. $20\text{ MeV}$
C. $2\text{ MeV}$
D. $2000\text{ MeV}$
Solution: Most of it appears as kinetic energy of the two fission fragments.
Q9 — Mass Defect & Binding Energy · hard · theory
Compared with fission, nuclear fusion releases:
A. Exactly the same energy per nucleon
B. Less energy per nucleon
C. More energy per nucleon ✓ Correct
D. No energy at all
Solution: Fusion of hydrogen into helium liberates about $6\text{ MeV}$ per nucleon against roughly $0.9\text{ MeV}$ for fission.
Q10 — Mass Defect & Binding Energy · hard · numerical
In the reaction $^2_1\text{H} + ^3_1\text{H} \to ^4_2\text{He} + ^1_0\text{n}$ the mass defect is $0.01888\text{ u}$. The energy released is approximately:
A. $200\text{ MeV}$
B. $20.0\text{ MeV}$
C. $17.6\text{ MeV}$ ✓ Correct
D. $14.1\text{ MeV}$
Solution: $Q = 0.01888 \times 931.5 \approx 17.6\text{ MeV}$.
Q11 — Mass Defect & Binding Energy · medium · numerical
A nuclear reaction has a mass defect of $0.1\text{ u}$. The energy released is approximately:
A. $931.5\text{ MeV}$
B. $0.1\text{ MeV}$
C. $9.315\text{ MeV}$
D. $93.15\text{ MeV}$ ✓ Correct
Solution: $E = 0.1 \times 931.5 = 93.15\text{ MeV}$.
Q12 — Mass Defect & Binding Energy · medium · numerical
The binding energy per nucleon of $^{56}_{26}\text{Fe}$ is approximately:
A. $7.6\text{ MeV}$
B. $1.1\text{ MeV}$
C. $8.8\text{ MeV}$ ✓ Correct
D. $12.4\text{ MeV}$
Solution: Iron-56 lies at the maximum of the binding energy curve, making it among the most stable of all nuclei.
Q13 — Mass Defect & Binding Energy · medium · numerical
A nucleus of mass number $56$ has a binding energy per nucleon of $8.8\text{ MeV}$. Its total binding energy is:
A. $492.8\text{ MeV}$ ✓ Correct
B. $64.8\text{ MeV}$
C. $56\text{ MeV}$
D. $8.8\text{ MeV}$
Solution: Total $BE = 56 \times 8.8 = 492.8\text{ MeV}$.
Q14 — Mass Defect & Binding Energy · medium · numerical
A mass defect of $0.5\text{ u}$ corresponds to an energy of approximately:
A. $465.8\text{ MeV}$ ✓ Correct
B. $931.5\text{ MeV}$
C. $46.6\text{ MeV}$
D. $0.5\text{ MeV}$
Solution: $E = 0.5 \times 931.5 \approx 465.8\text{ MeV}$.
Q15 — Mass Defect & Binding Energy · medium · numerical
The binding energy of a deuteron is about $2.2\text{ MeV}$. Its binding energy per nucleon is:
A. $0.55\text{ MeV}$
B. $2.2\text{ MeV}$
C. $1.1\text{ MeV}$ ✓ Correct
D. $4.4\text{ MeV}$
Solution: A deuteron has two nucleons, so $\dfrac{2.2}{2} = 1.1\text{ MeV}$ each — unusually loosely bound.
Q16 — Mass Defect & Binding Energy · medium · numerical
A mass defect of $0.002\text{ u}$ corresponds to an energy of approximately:
A. $0.186\text{ MeV}$
B. $1.86\text{ MeV}$ ✓ Correct
C. $931.5\text{ MeV}$
D. $18.6\text{ MeV}$
Solution: $E = 0.002 \times 931.5 \approx 1.86\text{ MeV}$.
Q17 — Mass Defect & Binding Energy · hard · numerical
A nucleus has a binding energy of $28\text{ MeV}$. Its mass defect is approximately:
A. $28\text{ u}$
B. $0.03\text{ u}$ ✓ Correct
C. $0.3\text{ u}$
D. $0.003\text{ u}$
Solution: $\Delta m = \dfrac{28}{931.5} \approx 0.03\text{ u}$.
Q18 — Mass Defect & Binding Energy · hard · numerical
An alpha particle has a binding energy of about $28.3\text{ MeV}$. Its binding energy per nucleon is approximately:
A. $28.3\text{ MeV}$
B. $7.07\text{ MeV}$ ✓ Correct
C. $14.15\text{ MeV}$
D. $4\text{ MeV}$
Solution: $\dfrac{28.3}{4} \approx 7.07\text{ MeV}$, which is why the alpha particle is exceptionally stable for a light nucleus.
Q19 — Mass Defect & Binding Energy · easy · numerical
Two nuclei have binding energies per nucleon of $7.5\text{ MeV}$ and $8.5\text{ MeV}$. The more stable one is:
A. Neither is stable
B. Both are equally stable
C. The nucleus with $7.5\text{ MeV}$ per nucleon
D. The nucleus with $8.5\text{ MeV}$ per nucleon ✓ Correct
Solution: Greater binding energy per nucleon means the nucleons are held more tightly.
Q20 — Mass Defect & Binding Energy · medium · numerical
The mass defect of a nucleus is $\Delta m$ kilogram. The binding energy in joule is:
A. $\Delta m \times 3 \times 10^8$
B. $\Delta m \times 931.5$
C. $\dfrac{\Delta m}{9 \times 10^{16}}$
D. $\Delta m \times 9 \times 10^{16}$ ✓ Correct
Solution: $BE = \Delta m\,c^2$ and $c^2 = 9 \times 10^{16}\text{ m}^2/\text{s}^2$.
Q21 — Mass Defect & Binding Energy · hard · numerical
The energy released per fission of uranium-235 is about $200\text{ MeV}$. The number of fissions needed to release $1\text{ J}$ is approximately ($1\text{ MeV} = 1.6 \times 10^{-13}\text{ J}$):
A. $200$
B. $3.1 \times 10^{10}$ ✓ Correct
C. $3.1 \times 10^{13}$
D. $6.25 \times 10^{18}$
Solution: Each fission gives $200 \times 1.6 \times 10^{-13} = 3.2 \times 10^{-11}\text{ J}$, so $N = \dfrac{1}{3.2 \times 10^{-11}} \approx 3.1 \times 10^{10}$.