If the activation energy of a reaction is 80.9 kJ mol$$^{-1}$$, the fraction of molecules at 700 K, having enough energy to react to form products is $$e^{-x}$$. The value of $$x$$ is (Rounded off to the nearest integer) [Use R = 8.31 J K$$^{-1}$$ mol$$^{-1}$$]

The fraction of molecules having energy equal to or greater than the activation energy $$E_a$$ is given by the Boltzmann factor: $$f = e^{-E_a/(RT)}$$.

We are given $$E_a = 80.9$$ kJ/mol $$= 80900$$ J/mol, $$T = 700$$ K, and $$R = 8.31$$ J K$$^{-1}$$ mol$$^{-1}$$.

Computing the exponent: $$x = \frac{E_a}{RT} = \frac{80900}{8.31 \times 700} = \frac{80900}{5817} = 13.908$$.

Rounded to the nearest integer, $$x = 14$$.

Therefore, the fraction of molecules with enough energy is $$e^{-14}$$, and the value of $$x$$ is $$14$$.