Question

Suppose, we think of fission of a `._26Fe^(56)` nucleus into two equal fragments `._13Al^(28)`. Is the fission energetically possible? Argue by working out Q of the process. Given `m(._26Fe^(56))=55.93494u, m(._13Al^(28))=27.98191 u.`

Answer 1

the fission of `""_(26)^(56)Fe` can be given as :
`""_(13)^(56)Fe to 2 _(13)^(28 Al`
It is given that :
Atomic mass of `m(""_(26)^(56)Fe ) =55.93494 u`
Atomic mass of `m(""_(13)^(28)Al)=27.98191u`
the Q- value os this nucleae rection is given as :
`Q=[m(""_(26)^(56)Fe)-2m (_(13)^(28)Al)]c^(2)`
` =[55.93494 -2xx27.98191]c^(2)`
` =(-0.02888c^(2))u`
But 1 u `=931.5 MeV//c^(2)`
` therefore Q=- 0.02888 xx931.5=-26.902 Mev`
the Q -value of the fission is nagative , therefore the fission in not possible entergetically . for an energetically -possible fission reaction , the Q - value must be posstive .