Lesson / Chemistry / Oxygen

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Notes on Oxygen

211 / May-30-2021 12:28:53 By- srijan /

Symbol: 'O'
Atomic Number: '8'
Atomic Mass: '16 amu'
Valency: '2'
Electronic Configuration: '1s2 2s22p41p' (P- block element
Isotopes: 168O (Must abundent o the earth surface) , 178O , 188O (Radioactive)

The binary compound of oxygen with any other elements are called oxides. For examples: CO, CO2, SO2 ,SO3 , H2O, CaO, ZnO , BaO2 etc. The compound such as Ca(OH)2, CaCO3, NaHCO3 etc. The compounds such as CaHCO3, CaCO3 etc are not termed as oxides because oxygen is in combination with more than one elements.

Classification of oxides:
On the basis of chemical behaviour and amount of oxygen oxide may be classified into the following groups:

i) Acidic Oxides( Oxides of non - metals ): Those oxides which gives acid when dissolved in water or give salts and water with base are called acidic oxides. For examples: SO2, SO3, CO2, P2O5, CrO3, etc

CO2 + H2O → H2CO3 (carbonic acid)
CO2 + 2NaOH → Na2CO3 + H2O
SO2 + H2O → H2SO3 (sulphurous acid)
P2O5 + 3 H2O → 2H3PO4( Phosphoric acid )
2N2 + H2O → HNO3 + HNO2

ii) Basic Oxides(Oxides of metal):
Those oxides which give base when dissolves in water or gives salts and water with acid, are called basic oxides. For example: CaO, MgO, BaO, Na2O, etc

CaO + 2HCl → CaCl2 + H2O
MgO + H2SO4 → MgSO4 + H2O
Na2O + H2O → 2NaCl + H2O
Na2O + H2O → 2NaOH
CaO + H2O → Ca(OH)2

iii) Amphoteric Oxides:
Those oxides exibite the properties of both acidic and basic oxides are called amphoteric oxides. For examples: ZnO, Al2O3, SnO2 , SnO, PbO2, PbO, etc.

1) ZnO(basic Oxides) + 2 HCl → ZnCl2 + H2O
ZnO(Acidic Oxides) + 2NaOH → Na2ZnO2 (Sodium zincate) + H2O

2) Al2O3(Basic) + 2 NaOH → 2NaAlO2 ( Sodium Aluminate ) + H2O
Al2O3(Acidic) + 2NaOH → 2NaAlO2 (Sodium meta - aluminate) + H2O

iv) Neutral Oxides:
Those oxides which are neither acidic or basic are called neutral oxides. For example: H2O, NO, CO, N2O, etc.

Classification based on oxygen contental

i) Normal oxides:
Those oxides which have oxygen content as required by the valence rules are called normal oxides. for eg: CO2 , SO3, PbO, MnO, P2O5, etc

Poly Oxides:
Those oxide whic have greater oxygen content then that required by the valency rules are called poly oxides. It is up two types.

a) Peroxides:
Those oxides which give hydrogen peroxides with dilute acid and oxygen gas with conc. H2SO4 are called peroxides. For eg: Na2O2, BaO2, Li2O2, etc.

BaO2 + H2SO4(dil) → BaSO4 + H2O2(Hydrogen Peroxide)
2BaO2 + H2SO4(conc) → 2 BaSO4 + H2O + O2
These oxides contain (O2)-2 ion having oxidation number of oxygen as -1.

b) DIoxide:
Those polyoxide which don't give hydrogen peroxide with dilute acid are called dioxides. For examples: MnO2 , PbO2 etc

MnO2 + 4HCl (conc) → MnO2 + 2H2O + Cl2

2MnO2 + 2H2SO4(Conc) → MnSO4 + 2H2O + O2

iii) Sub- Oxides:
Those oxides which have lower oxygen content that required by the valency rule are called sub - oxides. For examples: N2O , PbO2 , C3O2 etc.

iv) Mixed Oxides:
Those oxides which behaves as a mixture os two simple oxides, are callled mixed oxide. FOr eg: Fe3O4, Pb3O4, Mn3O4, etc.
For eg: red lead (pb3O4) = 2 pbo (Normal Oxide)+ pbo2(dioxide)

v) Super Oxides:
Those oxides which contain higher number of oxygen in which the oxidation number of oxygen is -1/2 are known as super oxides. For eg: KO2, RbO2, CSO2, etc.