Answer:
[tex]470\frac{KJ}{mol}[/tex]
Explanation:
The activation energy represents the energy barrier that reagents must pass to transform into products (or products to transform into reagents in a reverse reaction)
For any reaction, the change in enthalpy is related to the activation energy by the equation
[tex]\Delta H =E_{a\ direct}-E_{a\ reverse}[/tex]
So, the activation energy for the reverse reaction is
[tex]E_{a\ reverse}=E_{a\ direct}-\Delta H =218 \frac{KJ}{mol} - (-252)\frac{KJ}{mol}=470\frac{KJ}{mol}[/tex]