# Exothermic reaction [closed]

Please someone explain me the solution of this question.

## closed as off-topic by Jannis Andreska, Todd Minehardt, airhuff, Jon Custer, jerepierreMar 15 '17 at 16:47

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Now we see that $\ce{A + B -> X}$ is the slow step or rate determining step of the reaction, so it needs a higher activation energy than the step $\ce{X -> AB}$.