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Nuclear Fission of 1g of Uranium 235

  • Thread starter deezer
  • Start date
  • #1
18
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Homework Statement



What is the amount of energy released when 1g of uranium 235 undergoes fission? Fission of uranium is: uranium + n -> Ba + Kr +12n.

Homework Equations



E=Δmc^2

The Attempt at a Solution



I found the mass of the reactants to be 236.05256u and the products to be 235.92392u.
Thus Δm=-0.12864u

There are 2.56207x10^21 nuclei in 1g.

Therefore the energy needed is -165.122 J/g using E=Δmc^2. Is this the correct answer?
 

Answers and Replies

  • #2
1,506
17
You need to convert the Δm into kg using the information that 1u = 1.66 x 10^-27kg
Then use E = mc^2 with this mass in kg (c = speed of light 3 x 10^8m/s)
This is the energy released by each fission of U235.
Multiply by the number of nuclei undergoing fission.
 
  • #3
18
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Sorry clicked submit. Look below
 
Last edited:
  • #4
18
0
You need to convert the Δm into kg using the information that 1u = 1.66 x 10^-27kg
Then use E = mc^2 with this mass in kg (c = speed of light 3 x 10^8m/s)
This is the energy released by each fission of U235.
Multiply by the number of nuclei undergoing fission.
I did convert u to kg. I got -165.122 J/g, which I think is really low for Uranium. Can you check my answer? Is my change in mass right?
 
  • #5
1,506
17
Your Δm =0.12864u when converted to kg becomes 0.12864 x 1.66 x 10^-27 kg
=2.14 x 10^-28kg. This is the mass to use in E = mc^2
This is the energy released in 1 fission.
For 1g of material multiply by the number of atoms in 1g (I agree with the number you got)
When I did the calculation I got 49.2J
 
Last edited:

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