Can anyone help w/ this fission problem?

[smij44]

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?

 

[OlderDan]

How many amus are there for a 235U?

 

[xanthym]

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)


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[smij44]

ahh... thank you very much good sir