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If the bond energies of \( \mathrm{H}-\mathrm{H}, \mathrm{Br}-\mathrm{Br} \) and \( \mathrm{H}-\mathrm{Br} \) are \( 433,192 \) and \( 364 \mathrm{~kJ} \mathrm{~mol}^{-1} \) respectively, then
\( \Delta \mathrm{H}^{\circ} \) for the reaction :
\( \mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g) \rightarrow 2 \mathrm{HBr}(g) \)
Options:
\( \Delta \mathrm{H}^{\circ} \) for the reaction :
\( \mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g) \rightarrow 2 \mathrm{HBr}(g) \)
Solution:
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Verified Answer
The correct answer is:
\(- 103 \mathrm{~kJ} \)
For the reaction, \(\mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g) \rightarrow 2 \mathrm{HBr}(g)\)
\(\Delta \mathrm{H}^{\circ}\) reaction \(=\Sigma \Delta \mathrm{H}_{\text {bonds booken (reactants) }}-\Sigma \Delta \mathrm{H}_{\text {bonds formed (products) }}\)
\(=\left(433+192-2 \times 364 \mathrm{~kJ} \mathrm{~mol}^{-1}\right)\)
\(=-103 \mathrm{~kJ} \mathrm{~mol}^{-1}\)
\(\Delta \mathrm{H}^{\circ}\) reaction \(=\Sigma \Delta \mathrm{H}_{\text {bonds booken (reactants) }}-\Sigma \Delta \mathrm{H}_{\text {bonds formed (products) }}\)
\(=\left(433+192-2 \times 364 \mathrm{~kJ} \mathrm{~mol}^{-1}\right)\)
\(=-103 \mathrm{~kJ} \mathrm{~mol}^{-1}\)
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