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5. Thermodynamics and thermochemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry5. Thermodynamics and thermochemistry1 Mark
MCQ
The $H - H$ bond energy is $ 430\, kJ $ $mol$ and $Cl - Cl$ bond energy is $240\,kJ\,mo{l^{ - 1}}.\,\,\Delta H$ for $HCl$ is $ - 90\,kJ$. The $H - Cl$ bond energy is about.....$kJ\,mo{l^{ - 1}}$
  • A
    $180$
  • B
    $360$
  • C
    $213$
  • ✓
    $425$
✓

Answer

Correct option: D.
$425$
(d) $\frac{1}{2}{H_2} + \frac{1}{2}C{l_2} \to HCl,\,\,\,\Delta H = - 90\,KJ$
$\therefore \Delta H = \frac{1}{2}{E_{H - H}} + \frac{1}{2}{E_{Cl - Cl}}$
or $ - 90 = \frac{1}{2} \times 430 + \frac{1}{2} \times 240 - {E_{HCl}}$
$\therefore {E_{H - Cl}} = 425\,kJ\,mo{l^{ - 1}}$.

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