After absorbing a neutron, a Uranium-235 nucleus can fission to produce Barium-141 and krypton-92. Calculate the energy that would be released from this fission of a Uranium-235 atom. How do you work this out?

2 Answers
May 8, 2017

1.81*10^17 J

Explanation:

To solve this question we require some extra information which is not provided but I will take variables in place of them .

1^(st) method :

Mass defect method
we must be given the mass of protons and that of neutrons which is not provided so we will take the values provided over internet .

1 "Proton"=1.00727"amu"
1 "Neutron"=1.00866 "amu"

Net mass of U^235=92*1.00727+143*1.00866=236.90722 U

similarly we calculate the mass of barium and krypton ,
Ba^141=56*1.00727+85*1.00866=142.14322 U
Kr^92=36*1.00727+56*1.00866=92.74668 U

Mass defect(DeltaM) =236.90722 -142.14322-92.74668=2.01732 U
now according to Einsteins mass energy relation we know

E=Mc^2

it can be written as E=DeltaMc^2=(M(U^235)-M(Ba^141)-M(Kr^92))c^2=2.01732*(3*10^8)=1.81*10^17 J
this is the case when both the daughter nuclei are not radioactive but if they are we subtract the mass of two neutrons and then multiply by c^2.

May 8, 2017

For the reaction stated, the mass defect is:

Delta m = (m_U + m_n) - (m_(Ba) + m_(Kr))

Using rounded amu figures found on Wikipedia:

= ( (235.044 + 1.008) - (140.914 + 91.926) )

approx 3.212 \ "amu"

A mass of 1 amu converts to energy via E = mc^2 as: 1 "amu" approx 931 MeV

So here:

E approx 3 GeV

That's about 4.8 xx 10^(-7) J