In gaseous reaction, important for the understanding of the upper atmosphere `H_(2)O` and O react bimolecularly to from two OH readicals. `DeltaH` for this reaction is 72 kJ at 500 K and `E_(a)` is 77 kJ `"mol"^(-1)`, then `E_(a)` for the bimolecular recombination of two OH readicals to form `H_(2)O` and O is :

Options

A. `3 kJ mol^(-1)`
B. `4 kJ mol^(-1)`
C. `5 kJ mol^(-1)`
D. `7 kJ mol^(-1)`

Explanation

`H_2O + O to 2OH, DeltaH = 72 kJ" at " 500 K, [ :' E_(a(f))]`
Given `E_a= 77 kJ mol^(-1)`
`2OH to H_2O + O`, `:'[E_(a(b))]`
`E_(a(f))-E_(a(b))= DeltaH`
`:. = 77 -72`
`:. E_(a(b))= 5 kJ mol^(-1)`