Reactions involving Oxidation: Under the influence of ultraviolet light, ozone is capable of oxidizing dry hydrogen, the following reactions taking place: (i) 2O3 -----> 3O2; (ii) H2 + O3 ----> H2O + O2. Decomposition : Pure ozone decomposes on heating above 475 K to form O2 gas. 475 K 2O3 ————> 3O2 ΔH = –285.4 kJ Formation of ozonides : Ozone reacts with alkenes in the presence of CCl4 to form an ozonide.