Question

Binding energy per nucleon versus mass number curve for
nuclei is shown in figure. W, X, Y and Z are four nuclei
indicated on the curve. The process that would release
energy is

• A. $Y \rightarrow 2Z$
• B. $W \rightarrow X + Z$
• C. $Y \rightarrow 2Y$
• D. $X \rightarrow Y + Z$

Answer 1

Answer: (C)

Energy is released in a process when total binding energy of
the nucleus (= binding energy per nucleon $\times$ number of
nucleons) is increased or we can say, when total binding
energy of products is more than the reactants. By calculation
we can see that only in option (c), this happens.
Given : $W \rightarrow 2Y$
Binding energy of reactants$=120 \times 7.5=900 MeV$
and binding energy of products=$2 (60 \times 8.5)$
=1020 $MeV > 900 MeV$