Mass Defect MCQs for NEET

The actual mass of the nucleus is lesser than the sum of the individual mass of the nucleons because energy is ejected when the nucleus is created. The mass that is missing from the final nucleus is called the mass defect. Once the value of mass defect is known, the nuclear binding energy can be calculated using the formula.

E=(Δm)C²

Here Δm is the mass defect.

Q1: If the radius of the ₁₃Al²⁷ nucleus is taken to be R^Al then the radius of ₅₃Te¹²⁵ nucleus is nearly

1. (53/13)^1/3R_Al
2. 5/3 R_Al
3. ⅗ R_Al
4. (13/53) ^⅓ R_Al

Answer: (b) 5/3 R_Al

Q2: A nucleus of uranium decays at rest into nuclei of thorium and helium. Then,

1. The helium nucleus has more kinetic energy than the thorium nucleus
2. The helium nucleus has less momentum than the thorium nucleus
3. The helium nucleus has more momentum than the thorium nucleus
4. The helium nucleus has less kinetic energy than the thorium nucleus

Answer: (a) The helium nucleus has more kinetic energy than the thorium nucleus

Q3: The binding energy per nucleon of 3Li7 and 2He4 nuclei are 5.60 meV and 7.06meV respectively.

In the nuclear reaction 3Li7 + 1H1 ➡️ 2He4 +2He4+Q, the value of energy Q released is

1. 19.6 MeV
2. -2.4 MeV
3. 8.4 MeV
4. 17.3 MeV

Answer: (d) 17.3 MeV

Q4: Calculate the mass defect(amu/atom) for a ³⁷Cl atom for which the actual mass is 36.966 amu.

1. 0.341 amu
2. 0.388 amu
3. 0.623 amu
4. 0.264 amu

Answer: (a) 0.341 amu

Q5: The mass defect for an isotope is 0.410 amu/atom. Calculate the value of binding energy.

1. 1.23 x 10²⁰ kJ/mol
2. 2.23 x 10³ kJ/mol
3. 3.69 x 10¹⁰ kJ/mol
4. 3.69 x 10¹³ kJ/mol

Answer: (c) 3.69 x 10¹⁰ kJ/mol

Q6: Which isotope below has the highest binding energy?

1. ⁴He
2. ¹⁶O
3. ³²S
4. ⁵⁵Mn

Answer: (d) ⁵⁵Mn

Q7: Which of the following sentences is incorrect?

1. Nuclear binding energy is the energy released in the formation of an atom from subatomic particles
2. It the nucleus was formed from initially separated protons and electrons then the amount of matter converted into energy was called Mass defect.
3. The total mass of protons and electrons in the atom.
4. The most stable nuclei are molecules with the highest binding energy.

Answer: (c) The total mass of protons and electrons in the atom

Q8: A nucleus has a mass number A, atomic number Z and a binding energy B. The mass of neutron and proton are m_n and m_p respectively and cis the speed of light.

Which of the following expressions correctly represents the mass of the nucleus?

1. (A – Z)m_n+Zm_p-B/c²
2. (A – Z)m_n+Zm_p+ B/c²
3. (A + Z)m_n+Zm_p– B/c²
4. (A + Z)m_n+Zm_p+ B/c²

Answer: (a) (A – Z)m_n+Zm_p-B/c²

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