Question

The above is a plot of binding energy per nucleon $E_b,$ against the nuclear mass M; A, B,C, D, E, correspond to different nuclei. Consider four reactions :
(i) $A+B\to C+\epsilon$
(ii) $C\to A+B+\epsilon$
(iii) $D+E\to F+\epsilon$
(iv) $F\to D+E+\epsilon ,$
where $\epsilon$ is the energy released. In which reactions $\epsilon$ positive?

• A. (i) and (iii)
• B. (ii) and (iv)
• C. (ii) and (iii)
• D. (i) and (iv)

Answer 1

Answer: (D)

(i) and (iv)

Lighter nuclei $A$ and $B$ can fuse to form a heavier nucleus C. In these fusion reactions, there is a mass defect giving rise to a release in energy. On the other hand, a heavy nucleus $F$ can be split into two nuclei $D$ and $E$ of moderate masses. In this fission reaction also, there is a mass defect which appears in the form of release of energy. Thus energy is released in the processes $\left(i\right)$ and $\left(iv\right)$.