Nuclei-Quiz-9

 

NUCLEI QUIZ-9

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Q1In the fusion reaction _1^2 He+ _1^2 H→ _2^3 He+ _0^1 n, the masses of deuteron, helium and neutron expressed in a.m.u. are 2.015, 3.017 and 1.009, respectively. If 1 kg of deuterium undergoes complete fusion, find the amount of total energy released (1 a.m.u.=931.5 meV/c^2)

•   ≈6.02×10^13 J
•   ≈5.6×10^13 J
•   ≈9.0×10^13 J
•   ≈0.9×10^13 J

Solution

Q2. Uranium ores contain one radium-226 atom for every 2.8×10^6 uranium-238 atoms. Calculate the half-life of _92 U^238, given that the half-life of _88 Ra^226 is 1600 years (_88 Ra^226 is a decay product of _92 U^238)

•   1.75×10^3 years
•   1600×238/92 years
•   4.5×10^9 years
•   1600×238 years

Solution

Q3 Atomic masses of two isobars _29^64 Cu and _30^64 Zn are 63.9298 u and 63.9292 u, respectively. It can be concluded from this data that

•   Both the isobars are stable
•   _ ^64 Zn is radioactive, decaying to _ ^64 Cu through β-decay
•   _ ^64 Cu is radioactive, decaying to _ ^64 Zn through β-decay
•   _ ^64 Cu is radioactive, decaying to _ ^64 Zn through γ-decay

Solution

 (c) Expected atomic mass of Cu must be less than that of zinc, but it is not so. So, it means Cu is radioactive and unstable and decays to Zn through β-decay

Q4 The half-life period of RaB(_82 Pb^214) is 26.8 min. The mass of one curie of RaB is

•   3.71×10^10 g
•   3.71×10^(-10) g
•   8.61×10^10 g
•   3.064×10^(-8) g

Solution

Q5. A nucleus with atomic number Z and neutron number N undergoes two decay processes. The result is a nucleus with atomic number Z-3 and neutron number N-1. Which decay processes took place?

•   Two β^- decays
•   Two β^+ decays
•   An α-decay and a β^- decay
•   An α-decay and a β^+ decay

Solution

Q6〖 _92 U〗^238 absorbs a neutron. The product emits an electron. This product further emits an electron. The result is

•   〖 _94 Pu〗^239
•   〖 _90 Pu〗^239
• 〖 _93 Pu〗^237
•   〖 _94 Pu〗^237

Solution

Q7. The percentage of quantity of a radioactive material that remains after 5 half-lives will be

•   31%
•   3.125%
•   0.3%
•   1%

Solution

Q8 A stationery Thorium nucleus (A=220,Z=90) emits an alpha particle with kinetic energy E_α. What is the kinetic energy of the recoiling nucleus?

•   E_α/108
•   E_α/110
•   E_α/55
•   E_α/54

Solution

Q9. An element A decays into an element C by a two-step process: A→B+He_2^4 and B→C+2e_(-1)^0

•   A and C are isotopes
•   A and C are isobars
•   B and C are isotopes
•   A and B are isobars

Solution 

(a) Isotopes A and C have same number of protons

Q10. A 5×10^(-4) Å photon produces an electron-positron pair in the vincinity of a heavy nucleus. Rest energy of electron is 0.511 MeV. If they have the same kinetic energies, the energy of each particle is nearly

•  1.2 MeV
•  12 MeV
• 120 MeV V
• 1200 MeV
  
  

Solution