Question

Complete the equation for the following fission process ${}_{92}{{U}^{235}}+{}_{0}{{n}^{1}}{{\to }_{38}}S{{r}^{90}}+$

$\begin{align}
  & \text{A}\text{.}{{\text{ }}_{54}}X{{e}^{143}}+{{3}_{o}}{{n}^{1}} \\
 & \text{B}\text{.}{{\text{ }}_{54}}X{{e}^{145}} \\
 & \text{C}\text{.}{{\text{ }}_{57}}X{{e}^{142}} \\
 & \text{D}\text{.}{{\text{ }}_{54}}X{{e}^{142}}+{{3}_{0}}{{n}^{1}} \\
\end{align}$

Answer 1

Hint: To solve this question we will use the concept that the total atomic number and the total mass number of the reactants and the products in a reaction is always conserved. Find out the total mass number and the atomic number of the reactants. Then try to compare it with the products and find the required answer.

Complete step by step answer:
When we write a nuclear reaction, the total mass number and the total atomic number of the reactants and the products should be the same. In the reaction given in the question, ${}_{92}{{U}^{235}}+{}_{0}{{n}^{1}}{{\to }_{38}}S{{r}^{90}}+$
The total atomic number of the reactants is, $Z=92+0=92$
Where, 92 is the atomic number of Xe and 0 is the atomic number of the neutron.

Again, in the right-hand side of the reaction, the total atomic number of the products should be 92.
We have the atomic number of Sr is 38. So, the total atomic number of the other products should be,
$92-38=54$

Again, the total mass number of the reactants in the reaction is, $A=235+1=236$
Again, the total mass number of the reactants also should be 236.
We have the mass number of Sr is 90. So, the total atomic number of the other reactants should be,
$236-90=146$
Now, considering the option $_{54}X{{e}^{143}}+{{3}_{o}}{{n}^{1}}$, the total mass number is $143+3\times 1=146$
Again, the total atomic number is $54+3\times 0=54$
So, for this option we will get the required number of atomic number and mass number for the given products.
So, according to the conservation of mass number and the atomic number of reactants and products the required products will be $_{54}X{{e}^{143}}+{{3}_{o}}{{n}^{1}}$.

The correct option is (A).

Note: For the option $_{54}X{{e}^{145}}$ the mass number is 145, which is less than the required number. So, it is a wrong option.
Again, for the option $_{57}X{{e}^{142}}$, both the mass number and the atomic are not the required number. So it is also a wrong option.
Also, for the option $_{54}X{{e}^{142}}+{{3}_{0}}{{n}^{1}}$, the atomic number is 54 but the total mass number is 145, which is not the required number. So, it is also not a correct option.