Why does 2Cl(g) have higher enthalpy than Cl2(g) in this reaction?

[Lion214]

2Cl(g)→Cl2(g) ΔH = -243.4 KJ

Which has the higher enthalpy under these conditions, 2 Cl (g) or Cl2 (g)?





At first, I thought they would have the same change in enthalpy, because if I make it a reverse reaction, their magnitude will be the same. Then I realized that the signs would reverse, making the change of enthalpy for the product positive. Apparently that was not the answer, as 2 Cl(g) has a higher change in enthalpy. I'm posting this because I want to know why that is?

 

[Borek]

Think in terms of the exo- and endothermic reaction. Where does the reaction heat come from?