Write a preparation of dioxygen.

Explanation

(i) Laboratory preparation :
(1) By thermal decomposition of salts such as chlorates, nitrates and permanganates.
`2KClO_(3) overset(Delta)underset(MnO_(2)) to 2KCl + 3O_(2)`
`2NaNO_(3) overset(Delta) to 2NaNO_(2) + O_(2)`
`2KMnO_(4) overset(Delta)to K_(2)MnO_(4) + MnO_(2) + O_(2)`
(2) By the thermal decomposition of the oxides of metals low in the electrochemical series and higher oxides of some metals.
`2Ag_(2)O(s) overset(Delta)to 4Ag_(s) + O_(2)(g)`
`2Pb_(3)O_(4)(s) overset(Delta) to 6PbO(s) + O_(2)(g)`
`2HgO(s) overset(Delta) to 2Hg(l) + O_(2)(g)`
By decomposition of hydrogen peroxide in presence of finely divided metals and manganese dioxide.
`2H_(2)O_(2)(g) overset(MnO_(2))to 2H_(2)O(l) + O_(2)(g)`
`MnO_(2)` acts as catalyst.
(ii) Commercial production : Industrially, dioxygen is obtained from air by first removing carbon dioxide and water vapour and the remaining gases are liquefied and fractionally distilled to give dinitrogen and dioxygen.
On large scale it is prepared by Electrolysis of acidulated water which releases hydrogen at cathode and oxygen at the anode.