Of the reactions involved in the photodecomposition of ozone (shown below) , which are exothermic? 1. O₂ (g) + hν → O (g) + O (g)
2. O (g) + O₂(g) + M (g) → O₃(g) + M^* (g)
3. O₃(g) + hν → O₂ (g) + O (g)
4. O (g) + O (g) + M (g) → O₂ (g) + M^* (g)

Question

Quizplus · Accepted Answer

Reactions 2 and 4 are exothermic because they involve the formation of chemical bonds, releasing energy. Reaction 2 forms ozone, and reaction 4 forms molecular oxygen, both of which release energy.

Of the Reactions Involved in the Photodecomposition of Ozone (Shown