Question:

The binding energy per nucleon of \(Li\) and \(He\) nuclei are \(5.60\, MeV\) and \(7.06\, MeV\) respectively. In the nuclear reaction \(^7_3Li+_1^1H \rightarrow  _2^4He + _2^4He+Q\) the value of energy Q released is

Updated On: Jun 23, 2024
  • 19.6 MeV
  • -2.4 MeV
  • 8.4 MeV
  • 17.3 MeV
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The Correct Option is D

Solution and Explanation

The correct answer is D:17.3MeV
Binding energy of \(^7_3Li\) nucleus 
=7 \(\times 5.60 MeV=39.2 MeV\) 
Binding energy of \(_2^4 He\)nucles 
=4 \(\times 7.06 MeV=28.24 MeV\) 
The reaction is 
\(^7_3Li + _1^1H \rightarrow \, 2(_2^4 He)+Q\)
\(\therefore  Q=2(BE \space of\space  _2^4He)-(BE \, of \space _3^7Li)\) 
=2 \(\times\)28.24 MeV-39.2 MeV 
=56.48 MeV-39.2 MeV 
=17.28 MeV
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Concepts Used:

Nuclear Physics

Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons

Radius of Nucleus

‘R’ represents the radius of the nucleus. R = RoA1/3

Where,

  • Ro is the proportionality constant
  • A is the mass number of the element

Total Number of Protons and Neutrons in a Nucleus

The mass number (A), also known as the nucleon number, is the total number of neutrons and protons in a nucleus.

A = Z + N

Where, N is the neutron number, A is the mass number, Z is the proton number

Mass Defect

Mass defect is the difference between the sum of masses of the nucleons (neutrons + protons) constituting a nucleus and the rest mass of the nucleus and is given as:

Δm = Zmp + (A - Z) mn - M

Where Z = atomic number, A = mass number, mp = mass of 1 proton, mn = mass of 1 neutron and M = mass of nucleus.