(a) You have the following substances :
`NH_(3), O_(2), Pt and H_(2)O`. Write equations for the preparation of
`N_(2)O` from these substances.
(b) Considering the fact that `N_(2)` makes up about 79% of the atmosphere,
why don't animals use the more abundant
`N_(2)` instead of `O_(2)` for biological reactions.

Explanation

(a) `{:(4NH_(3)(g)+5O_(2)(g)underset(1100 K)overset(Pt)(rarr)4NO (g) + 6 H_(2)O(l),,,2NO (g)+O_(2)(g) rarr 2NO_(2)(g)),(3NO_(2)(g)+H_(2)O(l) rarr 2HNO_(3)(aq)+NO(g),,,NH_(3)(g)+HNO_(3)(aq) rarr NH_(4)NO_(3) (aq)),(NH_(4)NO_(3)(aq)underset("at room temperature")overset("Vacuum evaporation")rarr NH_(4)NO_(3)(s),,,NH_(4)NO_(3)(s)overset(523 K)rarr N_(2)O(g) + 2H_(2)O (l)):}`
(b) Animals need large amount of energy to move around and maintain the body temperature. Therefore, to obtain the required energy, it is much easier for them to break weaker double bond (493.4 kJ `mol^(-)`)of `O_(2)` than breaking the much stronger triple bond (941.4 kJ `mol^(-)`) of `N_(2)`.