Give two methods of preparation of dioxygen in laboratory and give its uses ?

Explanation

Preparation of `O_2`
(i) `2Na_2 O_2 + 2H_2 O to 4NaOH + O_2`
(ii) `2KClO_3 overset(MnO Delta)to 2KCl + 3O_2`
(iii) `2KMnO_4 overset(Delta)to K_2 MnO_4 + MnO_2 + O_2`
Use o dioxygen
(i) For cutting and welding of metals
(ii) For the manufacture of steel
(iii) For the combustion of fuels (hydrogen, hydazine etc) in rockets.
(iv) For breathing in hospitals, high altitude flying, in mountaineering, for diving under water.