Question

The above is a plot of binding energy per nucleon $E_b$, against the nuclear mass M; A, B, C, D, E, F correspond to different nuclei. Consider four reactions;
[AIEEE-2009]

(i) A + B → C + E (ii) C → A + B + E
(iii) D + E → F + E (iv) F → D + E + E

Where $\epsilon$ is the energy released? In which reactions is $\epsilon$ positive?

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

Answer 1

The correct option is A (i) and (iv)

Look at the graph

Now, from the options, option (iii)
D + E → F + E

can be clearly ruled out, as D has much more binding energy them F.

Now, let us consider
(i) A + B → C + E
(ii) C → A + B + E
(iv) F → D + E + E
(iv) is obviously gonna release positive energy as F has much lesser. Binding energy / nuclear than C + E + F

Similarly (i) is also gonna have positive release of energy.

Whereas, (ii) is not, as A has a very less Binding energy.

i.e., (i) & (iv) are the answer.