Question

A typical fission reaction is given as
$${}_{92}{U}^{235}{+}_0{n}^1\to \left[{}_{92}{U}^{236}\right]{\to }_{z_1}{X}^{A_1}{+}_{z_2}{Y}^{A_2}+ϵ{}_0{n}^1$$ Which one of the following statement(s) is/are correct for above reaction?

• A. $z_1+z_2=92;A_1+A_2+ϵ=236$.
• B. The ratio of masses of $X\&Y$ is found experimentally to be roughly $3/2$.
• C. The number of neutrons $\left(ϵ\right)$ released in the fission of a particular element will depend upon the final fragments that are produced.
• D. The two decay fragments usually have a neutron-proton ratio approximately equal to that of the original nucleus.

Answer 1

Answer: (A), (B), (C), (D)

The two decay fragments usually have a neutron-proton ratio approximately equal to that of the original nucleus.

From the given reaction mechanism, $z_1+z_2=92\&A_1+A_2+ϵ=236$

By balancing the mass numbers and atomic numbers, we can assume $X$ and $Y$ to be any of the elements in the below, given two possible reactions.

$${}_{92}{U}^{235}{+}_0{n}^1{\to }_{54}{X}^{140}{+}_{38}{Y}^{94}+2{}_0{n}^1$$$${}_{92}{U}^{235}{+}_0{n}^1{\to }_{56}{X}^{144}{+}_{36}{Y}^{89}+3{}_0{n}^1$$So, the ratio of masses of $X\&Y$ is approximately equal to $\frac{3}{2}$.

It is evident that, the number of neutrons released in a fission reaction depends upon the final fragments $($two neutrons are released in the first event and three neutrons are released in the second event$)$.

To find the neutron-proton ratio of parent and daughter nuclei, we can say that daughter nuclei have $n/p$ ratio approximately equal to that of the original nucleus.

Hence, options $\left(A\right),\left(B\right),\left(C\right)$ and $\left(D\right)$ are the correct options.