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)

$Y \rightarrow 2Y$

Answer 2

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 $MeV > 900 MeV$