| (i) \[{{\Delta }_{f}}H{}^\circ \] of \[{{N}_{2}}O\] is \[82\text{ }kJ\text{ }mo{{l}^{-1}}\] |
| (ii) Bond energies of \[N\equiv N,N=N,O=O\] and \[N=O\] are 946, 418, 498 and \[607kJ\text{ }mo{{l}^{-1}}\] respectively, The resonance energy of \[{{N}_{2}}O\] is: |
A) \[-88kJ\]
B) \[-66kJ\]
C) \[-62kJ\]
D) \[~-\,44\,kJ\]
Correct Answer: A
Solution :
[a] \[{{N}_{2}}(g)+\frac{1}{2}{{O}_{2}}\to {{N}_{2}}O(g)\] \[N\equiv N\left( g \right)+\frac{1}{2}\left( O=O \right)\to \underset{\scriptscriptstyle\centerdot\centerdot}{\ddot{N}}=\overset{+}{\mathop{ }}\,=\ddot{\underset{\scriptscriptstyle\centerdot\centerdot}{O}}\left( g \right)\] \[\Delta {{H}_{f}}^{{}^\circ }=\] [Energy required for breaking of bonds]-[Energy released for forming of bonds] \[=(\Delta {{H}_{N\equiv N}}+\frac{1}{2}\Delta {{H}_{O=O}}-(\Delta {{H}_{N=N}}+\Delta {{H}_{N=O}})\] \[=\left( 946+\frac{1}{2}\times 498 \right)-\left( 418+607 \right)\] \[=170kJ\,mo{{l}^{-1}}\] Resonance energy \[=82-170\] \[=-88kJ\,mo{{l}^{-1}}\]
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