Question

The number of neutrons emitted when $_{92}^{235}U$ undergoes controlled nuclear fission to $_{54}^{142}Xe$ and $_{38}^{90}Sr$ is:
A. 0
B. 1
C. 2
D. 3

Answer 1

The given uranium nuclei reacts with a neutron to undergo controlled nuclear fission and the products of this reaction are $_{54}^{142}Xe$ and $_{38}^{90}Sr$ along with neutrons. By writing a balanced nuclear reaction, we can find out the number of neutrons which are produced in this reaction.

Complete answer:
In nuclear fission, an unstable nucleus undergoes fission during which it splits into lighter nuclei. This is achieved when an unstable nucleus is bombarded by neutrons.
In a controlled nuclear fission, we induce the fission by restricting the number of neutrons by slowing them down.
When a $_{92}^{235}U$ nuclei undergoes controlled nuclear fission, it produces the lighter nuclei $_{54}^{142}Xe$ and $_{38}^{90}Sr$ along with more neutrons.
Let us write the equation for this nuclear reaction.
$_{92}^{235}U + _0^1n \to _{54}^{142}Xe + _{38}^{90}Sr + _0^1n + energy$
This equation is not balanced. On the balancing the equation we get
$_{92}^{235}U + _0^1n \to _{54}^{142}Xe + _{38}^{90}Sr + 4_0^1n + energy$
Therefore, there are 3 neutrons produced in this reaction.

So, the correct answer is “Option D”.

Additional Information:
There are two types of nuclear reactions: Nuclear fission and nuclear fusion.
In nuclear fission, a heavy nucleus splits into lighter nuclei releasing a large amount of energy while in nuclear fusion, the lighter nuclei fuse together to form heavier nuclei releasing a large amount of energy.
Nuclear fusion requires a very large amount of energy to take place and on earth, we do not have any source of that much energy available so only nuclear fission is possible on earth since it occurs by itself and does not require additional energy to occur. Nuclear fusion is a main source of energy in the sun.

Note:
1. The balancing of a nuclear reaction is done by equating the number of protons and neutrons on each side.
2. The initial neutron is obtained unchanged after the reaction, so it is not counted in the total number of neutrons produced in the reaction.