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#