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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
The Nucleus

Concepts Of Physics MCQ Edition [Volume 2] · Physics · The Nucleus

Determine the amount of energy released during the reaction given...

Determine the amount of energy released during the reaction given below:
^{7}\text{Li} + p \to \alpha + \alpha.<br>Theatomicmassof7Li.<br>The atomic mass of ^{7}\text{Li} is 7.0160 u7.0160 \text{ u} and that of ^{4}\text{He}isis4.0026 \text{ u}.

Options

  1. A18.60 MeV18.60 \text{ MeV}
  2. B17.34 MeV17.34 \text{ MeV}
  3. C16.83 MeV16.83 \text{ MeV}
  4. D15.24 MeV15.24 \text{ MeV}

Correct answer

B. 17.34 MeV17.34 \text{ MeV}

Step-by-step solution

The nuclear reaction can be written using atomic masses as:

^{7}\text{Li} + ^{1}\text{H} \rightarrow 2 ^{4}\text{He}<br><br>Takingtheatomicmassofhydrogen1H<br><br>Taking the atomic mass of hydrogen ^{1}\text{H} as 1.00783 u1.00783 \text{ u}, the total mass of the reactants is:

mreactants=m(7Li)+m(1H)m_{\text{reactants}} = m(^{7}\text{Li}) + m(^{1}\text{H})

mreactants=7.0160 u+1.00783 u=8.02383 um_{\text{reactants}} = 7.0160 \text{ u} + 1.00783 \text{ u} = 8.02383 \text{ u}

The total mass of the products is:

mproducts=2×m(4He)m_{\text{products}} = 2 \times m(^{4}\text{He})

mproducts=2×4.0026 u=8.0052 um_{\text{products}} = 2 \times 4.0026 \text{ u} = 8.0052 \text{ u}

The mass defect Δm\Delta m is:

Δm=mreactants−mproducts\Delta m = m_{\text{reactants}} - m_{\text{products}}

Δm=8.02383 u−8.0052 u=0.01863 u\Delta m = 8.02383 \text{ u} - 8.0052 \text{ u} = 0.01863 \text{ u}

The energy released QQ is calculated by converting the mass defect into energy (using 1 u≈931 MeV/c21 \text{ u} \approx 931 \text{ MeV}/c^2):

Q=0.01863×931 MeV≈17.34 MeVQ = 0.01863 \times 931 \text{ MeV} \approx 17.34 \text{ MeV}

Answer: 17.34 MeV17.34 \text{ MeV}
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