OXIDES

OXIDES

Oxygen combines with elements to form oxides which are binary compounds of oxygen that can be classified into four groups:

1. Acidic Oxide
2. Basic Oxide
3. Amphoteric Oxide
4. Neutral Oxide

In addition, there are peroxides and other higher oxides.

a. Acidic Oxides

These are oxides of non-metals which react with water to produce acids. They also react with alkalis to form salt and water only. Oxides of non-metals which react with water to form acids are called anhydrides.

e.g.      CO₂ + H₂O                  H₂CO₃

                                    trioxocarbonate(iv)acid                                              

            SO₂ + H₂O                  H₂SO_3(aq)

                                    trioxosulphate(iv)acid

            SO_3(g) + H₂O                 H₂SO₄

                                    tetraoxosulphate(vi)acid

            P₄O_10(s) + 6H₂O_(l)                        4H₃PO_4(aq)

                                    tetraoxosulphate(v)acid

            2NO_2(g) + H₂O_(l)                       HNO₃ + HNO₂          

                                    trioxonitrate(v) and dioxonitrate(iii)

With Alkalis

CO_2(g) + 2KOH_(aq)                      K₂CO_3(aq) + H₂O_(l)

SO_2(g) + 2KOH_(aq)                        K₂SO_4(aq) + H₂O_(l)

SO_3(g) + 2NaOH_(aq)                               Na₂SO_4(aq) + H₂O_(l)

b. Basic Oxide:

These are oxides of metals which react with acids to form salt and water only.

e.g. Sodium oxide       Na₂O

       Potassium oxide   K₂O

       Magnesium oxide MgO

Copper(ii)oxide           CuO

       Calcium oxide                  CaO

They react with acids to form a salt and water only.

Na₂O + 2HCl_(aq)                                   2NaCl_(aq) + H₂O_(l)

K₂O + 2HCl_(aq)                                    2KCl_(aq) + H₂O_(l)

2CaO + 2HNO₃                      Ca(NO₃)_2(aq) + H₂O_(l)

c. Amphoteric oxides:

Are metallic oxides which can react with both acids and alkalis to produce salt and water only.

With acids, amphoteric acids behave as bases, forming a salt and water only.

ZnO_(s) + H₂SO_4(aq)                                          ZnSO_4(aq) + H₂O_(l)

Al₂O₃ + 6HCl_(aq)                                   2Al(Cl)_3(aq) + 3H₂O_(l)

PbO_(s) + H₂SO_4(aq)                             PbSO_4(s) + H₂O_(l)

e.g.      Zinc oxide       ZnO

            Aluminium oxide        Al₂O₃

            Lead(ii)oxide  PbO

            Tin(iv)oxide    SnO₂

With alkalis, they behave like acids and exhibit acidic property by forming complex salts.

ZnO_(g) + 2NaOH_(aq) + H₂O_(l)                                         Na₂Zn(OH)₄

                                                            sodiumtetrahydrozincate(iii)

Al₂O_3(s) + 2NaOH_(aq) + 3H₂O                                         2NaAl(OH)_4(aq)

                                                            sodiumtetrahydrooxoaluminate(iii)    

PbO_(s) + 2NaOH_(aq) + H₂O_(l)                                  Na₂Pb(OH)_4(aq)

                                                            sodiumtetrahydroxoplumbate(ii)

• Neutral oxide:

These are oxides of non-metal show neither acidic nor basic properties/behaviour.

e.g.

Nitrogen(I)oxide                     N₂O

Carbon(ii)oxide                       CO

         Water                             H₂O

EVALUATION:  mention 5 types of oxides with examples

                           Mention 3 properties of oxygen                         

ASSIGNMENT:  how is ozone produced