Answer:
![470(KJ)/(mol)](https://img.qammunity.org/2020/formulas/chemistry/college/3m69reg1xb23hoj0ey6ce00580zw8fol5z.png)
Step-by-step 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
![\Delta H =E_(a\ direct)-E_(a\ reverse)](https://img.qammunity.org/2020/formulas/chemistry/college/ux3xowu6zeit4bhvtvqpb35ts58t1gw4aw.png)
So, the activation energy for the reverse reaction is
![E_(a\ reverse)=E_(a\ direct)-\Delta H =218 (KJ)/(mol) - (-252)(KJ)/(mol)=470(KJ)/(mol)](https://img.qammunity.org/2020/formulas/chemistry/college/g0grcr1whdwguxih31cfpeasoyp4cvurqj.png)