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Alkali metals on combustion in excess of...

Alkali metals on combustion in excess of air form different type of oxides depending on the size of metal cations e.g . lithium forms mainly the oxide `Li_2O`, sodium forms peroxide and some super oxides `NaO_2` and potassium, Rubidium and caesium form the superoxides, `MO_2`. The stability of peroxide and superoxide increases, as the size of the metal cation
increases because of the stabilisation of larger anion by larger cations through lattice energy effect. These oxides are easily hydrolysed by water. The oxides and the peroxides are colourless when pure, but the superoxides are yellow or orange in colour. Peroxide and superoxide of sodium and potassium are widely used as oxidising agent and as air purifier in space capsules, submarines and breathing mask. When sodium reacts with excess of oxygen at `350^@ C`, the oxidation number of oxygen per atom changes from:

A

0 to `-1`

B

0 to `-1/2`

C

`-1` to `-2`

D

`+1` to `-1`

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The correct Answer is:
A
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Alkali metals on combustion in excess of air form different type of oxides depending on the size of metal cations e.g . lithium forms mainly the oxide Li_2O , sodium forms peroxide and some super oxides NaO_2 and potassium, Rubidium and caesium form the superoxides, MO_2 . The stability of peroxide and superoxide increases, as the size of the metal cation increases because of the stabilisation of larger anion by larger cations through lattice energy effect. These oxides are easily hydrolysed by water. The oxides and the peroxides are colourless when pure, but the superoxides are yellow or orange in colour. Peroxide and superoxide of sodium and potassium are widely used as oxidising agent and as air purifier in space capsules, submarines and breathing mask. Which of the following compound is used in the emergency breathing apparatus ?

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