It does not burn itself but helps in burning. It is quite stable in nature and its bond dissociation energy is very high. Therefore, it is not very reactive as such, O2 —> O + O.
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Therefore, dioxygen reacts at higher temperatures. However, once the reaction starts, it proceeds of its own. This is because the chemical reactions of dioxygen are exothermic and the heat produced during the reaction is sufficient to sustain the reactions.
(1) Action with litmus :Like dihydrogen, it is also neutral and has no action on blue or red litmus.
(2)Reaction with metals : Active metals like Na, Ca react at room temp. to form their respective oxides.
4 Na + O2 —> 2Na2O
; 2Ca + O2 —> 2CaO
It reacts with Fe, Al, Cu etc. metals at high temperature
4 Al + 3O2 —> 2 Al2O3
; 4Fe + 3O2 —> 2Fe2O3
(3) Action with Non-metals : It form oxides.
1073 K
2H2 + O2 ——————> 2H2O;
Electric discharge
3273 K
N2 + O2 ——————> 2NO
Nitricoxide
Heat Heat
S + O2 ———> SO2; C + O2 ———> CO2;
(4) Reaction with compounds : Dioxygen is an oxidising agent and it oxidises many compounds under specific conditions. e.g.
700 K
4 HCl + O2 ————> 2H2O + 2Cl2;
CuCl2
1073 K
4 NH3 5 O2 ————> 4NO + 6H2O
Pt
Heat
CS2 + 3 O2 ————> CO2 + 2SO2
CH4 + 2 O2 ————> CO2 + 2H2O
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