Question

A chemical process occurring in two steps, is plotted as
The correct statement is:

• A. Endothermic,
  $A+B\to X$ (slow)
  $X\to AB$ (fast)
• B. Exothermic
  $A+B\to X$ (slow)
  $X\to AB$ (fast)
• C. Exothermic:
  $A+B\to X$ (fast)
  $X\to AB$ (slow)
• D. Enothermic
  $A+B\to X$ (fast)
  $X\to AB$ (slow)

Answer 1

The correct option is B Exothermic

$A+B\to X$ (slow)
$X\to AB$ (fast)
We know $\Delta H=E_f-E_b$

$\because$ $E_f$ is smaller than $E_b$ from the graph

Hence it is exothermic

$\Delta H=-ve$

Since $A+B\to X$ requires activation energy, Hence it is a show process.

Once the transition state is formed, it easily decomposes to product, hence a fast step.