Exothermic Determined

[Talia Leano 2H]

How can you determine this will be an exothermic reaction given this information: X ₂ (g) -> 2X (g) (X is a halogen)

[Mohamed Mido]

Although it takes energy to break bonds, halogens are more stable as single atoms rather than molecules because of the filled octet and other factors. So breaking a bond to take them back to their more stable and favored state is not energy-consuming but rather it gives off energy, meaning it's exothermic.

[Natalie Do 3F]

In almost all other scenarios, this reaction will be endothermic because, like what Mohamed said, forming bonds is exothermic and breaking bonds is endothermic. So often going from X2->2X will be an endothermic reaction.

[Gwirnowski 3B]

In most cases, any breaking of bonds is going to be an endothermic reaction as the system requires energy to break the bonds. However for halogens it will be energetically favorable to return to an un-bonded state, meaning that it will release energy to return to that state.

[Shreyank Kadadi 3K]

In general, the breaking of bonds requires energy whereas the forming of bonds releases energy. Since there is a bond being broken and no bonds are being formed, the reaction must be endothermic.

[Kaleb Tuliau 3E]

So going from Cl2 to 2Cl would be endothermic?

[Mackenzie Van Val 3E]

So going from Cl2 to 2Cl would be endothermic?

Yes, this would be endothermic. The only bond change occurring is that a bond is being broken, which requires energy, thus making it endothermic.