An endothermic reaction, $A \rightarrow B$ has an activation energy as $x \mathrm{~kJ} / \mathrm{mol}$. If the energy change of the reaction is $y \mathrm{~kJ}$, the activation energy of the reverse reaction is

• A

  $-x$
• Correct answer
  B

  $x-y$
• C

  $x+y$
• D

  $y-x$

Solution

Consider the following graph,

From the above graph $$ \begin{aligned} x &=y+E_{a, b} \\ E_{a, b} &=x-y \mathrm{~kJ} \end{aligned} $$

Hence, the correct answer is option: 'B'.