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Elements of Groups 16, 17 and 18 — Chemistry STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElements of Groups 16, 17 and 183 Marks
Question
Explain the laboratory methods for the preparation of dioxygen.
✓

Answer

(i) By heating chlorates, nitrates and permanganates.
Potassium chlorate in the presence of manganese dioxide on heating decomposes to form potassium chloride and oxygen.
$2 KClO _3 \xrightarrow[ MnO _2]{\Delta} 2 KCl +3 O _{2( g )}$
(ii) By the thermal decomposition of metal oxides.
$\begin{aligned}
& 2 Ag _2 O _{( s )} \xrightarrow{\text { heat }} 4 Ag + O _{2( g )} \\
& 2 HgO _{( s )} \xrightarrow{\text { heat }} 2 Hg + O _{2( g )} \\
& 2 PbO _{2( s )} \xrightarrow{\text { heat }} 2 PbO _{( s )}+ O _{2( g )}
\end{aligned}$
(iii) By the thermal decomposition of hydrogen peroxide :
The thermal decomposition of hydrogen peroxide in the presence of finely divided metal and manganese dioxide used as catalyst gives oxygen.
\92 H _2 O _{2 \text { (aq) }} \xrightarrow[ MnO _2]{\text { heat }} 2 H _2 O _{( l )}+ O _{2( g )}$

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