question_answer 109)

  Atomic hydrogen combines with almost all elements but molecular hydrogen does not. Explain.

Answer:

  Dihydrogen is not very reactive and does not react readily with other elements as its bond dissociation energy is the highest for single bond between two atoms of any element. Its dissociation energy is\[436kJ\,mo{{l}^{-1}}\]. The dissociation of dihydrogen is only 0.081% at 2000 K and it requires very high temperature for complete dissociation.                 \[{{H}_{2}}\xrightarrow[temperature]{V.high}2H\] There, most of the reactions of dihydrogen occur at high temperatures or in presence of some catalysts.