A) \[{{P}_{4}}\] is feasible but \[{{N}_{4}}\]is hot feasible
B) \[{{P}_{4}}\] is not feasible but \[{{N}_{4}}\] is feasible
C) Both \[{{P}_{4}}\] and \[{{N}_{4}}\] are feasible
D) Both \[{{P}_{4}}\] and \[{{N}_{4}}\]are not feasible
Correct Answer: A
Solution :
The process involves replacement of \[2\,(X\equiv X)\] units by \[6\,X-X\] bonds in the \[{{X}_{4}}\]tetrahedron. Energy is released when bonds are formed and thus species formed is stable. (i) \[2{{P}_{2}}(g)\xrightarrow{{}}{{P}_{4}}(g)\] \[\Delta {{H}_{f}}=-6\times BE\,(P-P)+2BE\,(P\equiv P)\] (BE = Bond energy) \[=-6\times 209+2\times 490\] \[=-274\,\,kJmo{{l}^{-1}}\] Formation of \[{{P}_{4}}\] is exothermic thus is feasible. (ii) \[2{{N}_{2}}(g)\xrightarrow{{}}{{N}_{4}}(g)\] \[\Delta {{H}_{f}}=-6\,BE\,(N-N)+2\,BE\,(N\equiv N)\] \[=-6\times 160+2\times 946\] \[=+932\,\,\,kJ\,\,mo{{l}^{-1}}\] Formation of \[{{N}_{4}}\] is endothermic, thus is not feasible.You need to login to perform this action.
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