Can anyone help w/ this fission problem?

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Homework Help Overview

The discussion revolves around a problem in nuclear physics, specifically relating to the energy released during the fission of uranium-235 and comparing it to the energy released from burning gasoline. The original poster attempts to calculate how many gallons of gasoline are needed to match the energy output from a specific mass of uranium-235 undergoing fission.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conversion of energy units from MeV to Joules and the calculation of energy released per fission reaction. There are questions about the number of atomic mass units (amus) in uranium-235 and the overall method for calculating the energy equivalence.

Discussion Status

Some participants have provided guidance on recalculating the energy based on the number of atoms in a mole of uranium-235 and clarified the energy release per atom. There is an acknowledgment of a misunderstanding regarding the calculation of energy per amu versus per atom.

Contextual Notes

The original poster's calculations involve assumptions about the conversion factors and the mass-energy equivalence, which are under scrutiny. The discussion reflects a need for clarity on these conversions and the relationships between the quantities involved.

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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:
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How many amus are there for a 235U?
 
smij44 said:
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?
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:
ahh... thank you very much good sir
 

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