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Question: Answered & Verified by Expert
The $\mathrm{H}-\mathrm{H}$ bond energy is $430 \mathrm{~kJ} \mathrm{~mol}$ and $\mathrm{Cl}-\mathrm{Cl}$ bond energy is $240 \mathrm{~kJ} \mathrm{~mol}^{-1} . \Delta \mathrm{H}$ for $\mathrm{HCl}$ is $-90 \mathrm{~kJ}$.
The $\mathrm{H}-\mathrm{Cl}$ bond energy is about
ChemistryThermodynamics (C)JEE Main
Options:
  • A $180 \mathrm{~kJ} \mathrm{~mol}^{-1}$
  • B $360 \mathrm{~kJ} \mathrm{~mol}^{-1}$
  • C $213 \mathrm{~kJ} \mathrm{~mol}^{-1}$
  • D $425 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Solution:
1772 Upvotes Verified Answer
The correct answer is: $425 \mathrm{~kJ} \mathrm{~mol}^{-1}$
$\frac{1}{2} \mathrm{H}_2+\frac{1}{2} \mathrm{Cl}_2 \rightarrow \mathrm{HCl}, \Delta \mathrm{H}=-90 \mathrm{KJ}$
$\therefore \Delta H=\frac{1}{2} E_{H-H}+\frac{1}{2} E_{C-C]}$
or $-90=\frac{1}{2} \times 430+\frac{1}{2} \times 240-E_{H C}$
$\therefore E_{H-C}=425 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

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