Comment on the thermodynamic stability of `NO(g)`, given
`1/2N_(2)(g)+1/2O_(2)(g)rarr NO(g), Delta_(r)H^(Θ)=90 kJ mol^(-1)`
`NO(g)+1/2O_(2)(g) rarr NO_(2)(g), Delta_(r)H^(Θ)=-74 kJ mol^(-1)`

Explanation

The positive value of `Delta_(r)H` indicates that heat is absorbed during the formation of `NO_((g))`.
This means that `NO_((g))` has higher energy than the reactants `(N_(2) and O_(2))` Hence, `NO_((g))` is unstable.
The negative value of `Delta_(r)H` indicates that heat is evolved during the formation of `NO_(2(g)` from `NO_((g)) and O_(2(g))`. The product, `NO_(2(g))` is stabilized wiht minimum energy.
Hence, unstable `NO_((g))` changes to unstable `NO_(2(g)).`