Answer 1

Dioxygen is prepared by heating potassium chlorate (KClO₃) in presence of the catalyst, MnO₂.

\[\ce{\underset{\text{Potassium chlorate}}{2KClO_{3(s)}} ->[Heat][MnO2] 2KCl_{(s)} + \underset{\text{Dioxygen}}{3O_{2(g)}}}\]