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Homework Help: Can anyone help w/ this fission problem?

  1. Apr 26, 2005 #1
    A gallon of gasoline releases 1.91×108 J of energy when it is burned. How many gallons of gas must be burned to release the same amount of energy as is released when 1.87 lb of 235U undergoes fission. (Assume that each fission reaction in 235U releases 181 MeV.)

    I know this-

    # gal of gas * energy= energy from fission

    1.87 lbs= 2.478*10^27 amu

    i thought that the answer could be found by converting 181 MeV to Joules, which equals 2.896*10^-11, multiplying that answer by the amus which equals 7.17*10^16, and then dividing it all by the energy of the gas. Apparently i am wrong however.... any suggestions?
    Last edited: Apr 26, 2005
  2. jcsd
  3. Apr 26, 2005 #2


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    How many amus are there for a 235U?
  4. Apr 26, 2005 #3


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    You mistakenly tried calculating fission energy released per amu. In fact, 235U fission produces (approx) 181 MeV per 235U atom. Your overall method is correct. Recalculate using:
    a) {Mass of 1 Mole 235U} = (235 g)
    b) {Number Atoms 235U in 1 Mole 235U} = (6.023e23)

    Last edited: Apr 26, 2005
  5. Apr 27, 2005 #4
    ahh... thank you very much good sir
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