Q: A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the binding energy in the process is

216 MeV. Gain = 2 \times 120 \times 8.5 - 240 \times 7.6 = 2040 - 1824 = 216 MeV

Q: The energy equivalent of 0.5 g of a substance is

4.5 \times 10^{13} J. E = mc^2 = 0.5 \times 10^{-3} \times (3 \times 10^8)^2 = 4.5 \times 10^{13} J

Q: The binding energy per nucleon of ^{7}_{3}Li and ^{4}_{2}He nuclei are 5.60 MeV and 7.06 MeV, respectively. In the nuclear reaction ^{7}_{3}Li + ^{1}_{1}H \rightarrow\ ^{4}_{2}He + ^{4}_{2}He + Q, the value of energy Q released is

17.3 MeV. Q = 2(4 \times 7.06) - (7 \times 5.60) = 56.48 - 39.2 = 17.3 MeV

Q: A certain mass of hydrogen is changed to helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV)

6.675 MeV. Energy liberated = 0.02866 \times 931 = 26.7 MeV Per u (A = 4): \frac{26.7}{4} = 6.675 MeV

Q: Fusion reaction takes place at high temperature because

kinetic energy is high enough to overcome the coulomb repulsion between nuclei. At high temperature the kinetic energy of the nuclei is high enough to overcome the Coulomb repulsion between them, allowing fusion.

Q: The mass of a ^{7}_{3}Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of ^{7}_{3}Li nucleus is nearly

5.6 MeV. Binding energy = 0.042 \times 931 = 39.1 MeV Per nucleon: \frac{39.1}{7} \approx 5.6 MeV

Q: A nucleus ^{A}_{Z}X has mass represented by m(A, Z). If m_p and m_n denote the mass of proton and neutron respectively and BE the binding energy (in MeV), then

BE = [Zm_p + (A - Z)m_n - m(A, Z)]c^2. The mass defect is \Delta m = Zm_p + (A - Z)m_n - m(A, Z), so BE = [Zm_p + (A - Z)m_n - m(A, Z)]c^2

Q: The binding energy of deuteron is 2.2 MeV and that of ^{4}_{2}He is 28 MeV. If two deuterons are fused to form one ^{4}_{2}He, then the energy released is

23.6 MeV. Energy released = BE of products − BE of reactants = 28 - 2 \times 2.2 = 23.6 MeV

Question 1

A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the binding energy in the process is

Accepted Answer

216 MeV. Gain = 2 	imes 120 	imes 8.5 - 240 	imes 7.6 = 2040 - 1824 = 216 MeV

Question 2

The energy equivalent of 0.5 g of a substance is

Accepted Answer

4.5 	imes 10^{13} J. E = mc^2 = 0.5 	imes 10^{-3} 	imes (3 	imes 10^8)^2 = 4.5 	imes 10^{13} J

Question 3

When a uranium isotope ^{235}_{92}U is bombarded with a neutron, it generates ^{89}_{36}Kr, three neutrons and

Accepted Answer

^{144}_{56}Ba. Charge: Z = 92 - 36 = 56; mass: A = 235 + 1 - 89 - 3 = 144

The other product is ^{144}_{56}Ba.

Question 4

A nucleus of uranium decays at rest into nuclei of thorium and helium. Then,

Accepted Answer

the helium nucleus has more kinetic energy than the thorium nucleus. Momentum conservation gives both fragments equal and opposite momenta. Since KE = \frac{p^2}{2m} and m_{He} < m_{Th}, the helium nucleus has more kinetic energy.

Question 5

The binding energy per nucleon of ^{7}_{3}Li and ^{4}_{2}He nuclei are 5.60 MeV and 7.06 MeV, respectively. In the nuclear reaction ^{7}_{3}Li + ^{1}_{1}H \rightarrow\ ^{4}_{2}He + ^{4}_{2}He + Q, the value of energy Q released is

Accepted Answer

17.3 MeV. Q = 2(4 	imes 7.06) - (7 	imes 5.60) = 56.48 - 39.2 = 17.3 MeV

Question 6

A certain mass of hydrogen is changed to helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV)

Accepted Answer

6.675 MeV. Energy liberated = 0.02866 	imes 931 = 26.7 MeV

Per u (A = 4): \frac{26.7}{4} = 6.675 MeV

Question 7

Fusion reaction takes place at high temperature because

Accepted Answer

kinetic energy is high enough to overcome the coulomb repulsion between nuclei. At high temperature the kinetic energy of the nuclei is high enough to overcome the Coulomb repulsion between them, allowing fusion.

Question 8

The mass of a ^{7}_{3}Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of ^{7}_{3}Li nucleus is nearly

Accepted Answer

5.6 MeV. Binding energy = 0.042 	imes 931 = 39.1 MeV

Per nucleon: \frac{39.1}{7} \approx 5.6 MeV

Question 9

A nucleus ^{A}_{Z}X has mass represented by m(A, Z). If m_p and m_n denote the mass of proton and neutron respectively and BE the binding energy (in MeV), then

Accepted Answer

BE = [Zm_p + (A - Z)m_n - m(A, Z)]c^2. The mass defect is \Delta m = Zm_p + (A - Z)m_n - m(A, Z), so

BE = [Zm_p + (A - Z)m_n - m(A, Z)]c^2

Question 10

The binding energy of deuteron is 2.2 MeV and that of ^{4}_{2}He is 28 MeV. If two deuterons are fused to form one ^{4}_{2}He, then the energy released is

Accepted Answer

23.6 MeV. Energy released = BE of products − BE of reactants

= 28 - 2 	imes 2.2 = 23.6 MeV

Question 11

In any fission process the ratio \frac{	ext{mass of fission products}}{	ext{mass of parent nucleus}} is

Accepted Answer

less than 1. In fission some mass is converted into energy, so the total mass of the fission products is less than that of the parent nucleus — the ratio is less than 1.

Question 12

Fission of nuclei is possible because the binding energy per nucleon in them

Accepted Answer

decreases with mass number at high mass numbers. For heavy nuclides the binding energy per nucleon decreases with increasing mass number, making them relatively unstable and fissionable.

Question 13

In the reaction ^{2}_{1}H + ^{3}_{1}H \rightarrow\ ^{4}_{2}He + ^{1}_{0}n, if the binding energies of ^{2}_{1}H, ^{3}_{1}H and ^{4}_{2}He are respectively a, b and c (in MeV), then the energy (in MeV) released in this reaction is

Accepted Answer

c - a - b. Energy released = BE of products − BE of reactants = c - (a + b) = c - a - b

Question 14

m_p denotes the mass of a proton and m_n that of a neutron. A given nucleus of binding energy BE, contains Z protons and N neutrons. The mass m(N, Z) of the nucleus is given by

Accepted Answer

m(N, Z) = Nm_n + Zm_p - BE/c^2. BE = [Nm_n + Zm_p - m(N, Z)]c^2

m(N, Z) = Nm_n + Zm_p - \frac{BE}{c^2}

Question 15

If in a nuclear fusion process, the masses of the fusing nuclei be m_1 and m_2 and the mass of the resultant nucleus be m_3, then

Accepted Answer

m_3 < (m_1 + m_2). In fusion some mass (the mass defect) is converted into released energy, so m_3 < m_1 + m_2.

Question 16

Solar energy is mainly caused due to

Accepted Answer

fusion of protons during synthesis of heavier elements. In the sun, energy is produced by the fusion of four protons (hydrogen nuclei) into a helium nucleus, releasing enormous energy.

Question 17

The mass of proton is 1.0073 u and that of neutron is 1.0087 u (u = atomic mass unit). The binding energy of ^{4}_{2}He is (mass of helium nucleus = 4.0015 u)

Accepted Answer

28.4 MeV. \Delta m = (2 	imes 1.0073 + 2 	imes 1.0087) - 4.0015 = 0.0305 u

BE = 0.0305 	imes 931 = 28.4 MeV

Question 18

When a deuterium is bombarded on ^{16}_{8}O nucleus, an \alpha-particle is emitted, then the product nucleus is

Accepted Answer

^{14}_{7}N. ^{16}_{8}O + ^{2}_{1}H \rightarrow\ ^{A}_{Z}X + ^{4}_{2}He

Mass: A = 16 + 2 - 4 = 14; charge: Z = 8 + 1 - 2 = 7 — nitrogen ^{14}_{7}N.

Question 19

Which of the following are suitable for the fusion process?

Accepted Answer

Light nuclei. Light nuclei (A < 20) have relatively small binding energy per nucleon; combining them into a heavier nucleus raises it and liberates a large amount of energy.

Question 20

In nuclear fission process, energy is released because

Accepted Answer

total binding energy of products formed due to nuclear fission is more than the parent fissionable material. Energy is released when the binding energy per nucleon of the products increases — the total binding energy of the fission products exceeds that of the parent nucleus.

Nuclear Fission & Fusion and Binding Energy — NEET Physics PYQ MCQs with Solutions

Questions with solutions