Question

Difficulty: HardNuclear Fission and Nuclear Fusion
Consider the nuclear fusion reaction below:
\text{^{2}_{1}H} + \text{^{3}_{1}H} \rightarrow \text{^{4}_{2}He} + \text{^{1}_{0}n} + Q
Given the rest masses:
Mass of \text{^{2}_{1}H} = 2.0141\text{ u}
Mass of \text{^{3}_{1}H} = 3.0160\text{ u}
Mass of \text{^{4}_{2}He} = 4.0015\text{ u}
Mass of \text{^{1}_{0}n} = 1.0087\text{ u}
If 1 u=931 MeV1\text{ u} = 931\text{ MeV}, what is the total energy released (QQ) in this fusion reaction?
  1. 18.53 MeV18.53\text{ MeV}Answer
  2. B
    957.69 MeV957.69\text{ MeV}
  3. C
    2.96×1012 MeV2.96 \times 10^{-12}\text{ MeV}
  4. D
    18.5 MeV18.5\text{ MeV}

Answer

18.53 MeV18.53\text{ MeV}
The total initial mass of the reactants is 2.0141 u+3.0160 u=5.0301 u2.0141\text{ u} + 3.0160\text{ u} = 5.0301\text{ u}. The total final mass of the products is 4.0015 u+1.0087 u=5.0102 u4.0015\text{ u} + 1.0087\text{ u} = 5.0102\text{ u}. Subtracting the product mass from the reactant mass gives a mass defect of Δm=0.0199 u\Delta m = 0.0199\text{ u}. Multiplying this mass defect by the conversion factor 931 MeV/u931\text{ MeV/u} yields an energy release of 18.53 MeV18.53\text{ MeV}.

Step-by-Step Solution

1
Calculate the total mass of the reactants
Mass of reactants=2.0141 u+3.0160 u=5.0301 u\text{Mass of reactants} = 2.0141\text{ u} + 3.0160\text{ u} = 5.0301\text{ u}
The total initial mass must be determined from the sum of the masses of deuterium and tritium.
2
Calculate the total mass of the products
Mass of products=4.0015 u+1.0087 u=5.0102 u\text{Mass of products} = 4.0015\text{ u} + 1.0087\text{ u} = 5.0102\text{ u}
The total final mass includes both the helium nucleus and the released neutron.
3
Determine the mass defect (Δm\Delta m)
Δm=5.0301 u5.0102 u=0.0199 u\Delta m = 5.0301\text{ u} - 5.0102\text{ u} = 0.0199\text{ u}
Mass defect is the difference between the total initial mass and the total final mass.
4
Convert the mass defect into energy released (QQ)
Q=0.0199×931 MeV=18.5269 MeV18.53 MeVQ = 0.0199 \times 931\text{ MeV} = 18.5269\text{ MeV} \approx 18.53\text{ MeV}
Using the mass-energy equivalence factor 1 u=931 MeV1\text{ u} = 931\text{ MeV} yields the energy in MeV\text{MeV}.

Key Concept

Calculation of energy released in nuclear fusion reactions using mass defect
Estimated Time:2m 0s
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