Chemical properties

Basic oxides

1. Interaction with water. Oxides of alkaline (Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O) and alkaline-earth (CaO, SrO, BaO) metals form soluble bases - alkalis:

Li₂O + H₂O = 2LiOH;

Rb₂O + H₂O = 2RbOH;

CaO + H₂O = Ca(OH)_2;

BaO + H₂O = Ba(OH)₂.

2. Interaction with acidic oxides forming the salts:

K₂O + SO₂ = K₂SO₃;

SrO + N₂O₅ = Sr(NO₃)₂;

CuO + SO₃ = CuSO₄;

3BaO + P₂O₅ = Ba₃(PO₄)₂.

3. Interaction with acids forming the salts and water:

Na₂O + 2HNO₃ = 2NaNO₃ + H₂O

NiO + H₂SO₄ = NiSO₄ + H₂O

3MgO + 2H₃PO₄ = Mg₃(PO₄)₂ + 3H₂O.

Other basic oxides do not react with water directly.

Acidic oxides

1. The most of acidic oxides reacts with water forming the acids (except a few oxides like SiO₂, MoO₃, WO₃):

SO₃ + H₂O = H₂SO₄;

N₂O₅ + H₂O = 2HNO₃;

P₂O₅ + 3H₂O = 2H₃PO₄;

4NO₂ + O₂ + 2H₂O = 4HNO₃.

2. Interaction with basic acids with forming the salts:

N₂O₃ + Na₂O = 2NaNO₂;

P₂O₅ + 3CaO = 2Ca₃(PO₄)₂;

SO₃ + BaO = BaSO₄.

3. Interaction with bases forming the salts and water:

SO₃ + Ba(OН)₂ = BaSO₄ + H₂O;

N₂O₅ + 2КOН = 2KNO₃ + H₂O;

SiO₂+2NaOН = Na₂SiO₃ + H₂O.

Amphoteric oxides

Term Amphoteric (from Greek) means double-sided, mutual. Therefore amphoteric oxides occupy a position between basic and acidic oxides and display corresponding chemical properties.

1. Interaction with basic and acidic oxides forming the salts:

PbO + SO₃ = PbSO₄;

PbO + N₂O₅ = Pb(NO₃)₂;

Cr₂O₃ + 3SO₃ = Cr₂(SO₄)₃;

Cr₂O₃ + 3N₂O₅ = 2Cr(NO₃)₃;

Li₂O + PbO = Li₂PbO₂;

CaO + PbO = CaPbO₂;

3Li₂O + Cr₂O₃ = 2Li₃CrO₃;

Li₂O + Cr₂O₃ = 2LiCrO₂;

CaO + Cr₂O₃ = Ca₃(CrO₃)₂;

CaO + Cr₂O₃ = Ca(CrO₂)₂.

2. Interaction with acids forming the salts and water:

PbO+ 2 HCl = PbCl₂ + H₂O;

Al₂O₃ + 2 H₃PO₄ = 2AlPO₄ + 3H₂O.

3. Interaction with alkalis forming the salts and water:

Cr₂O₃ + 6KOH = 2K₃CrO₃ + 3H₂O;

MnO₂ + 2NaOH = Na₂MnO₃ + H₂O.

Peroxides may be shown as a peculiar group of Oxygen-contained compounds. Frequently peroxides are considered as salts of Hydrogen peroxide H₂O₂, where O₂^-2 (-O-O-) is an analogue of acid residue. For example, BaO₂ - Barium peroxide includes Ba²⁺ and formally O^-.

Bases

Bases are complex substances, in which atoms of metals or ionic groups (for example, NH₄⁺) are bonded with one or several hydroxyls groups.

Classification of bases: they are divided into two groups - soluble in waters (alkalis - LiOH, NaOH, KOH, RbOH, CsOH, FrOH, Ca(OH)₂, Ba(OH)₂, Sr(OH)₂) and insoluble (for example, Fe(OH)₂, Cu(OH)₂ etc.). Insoluble bases include amphoteric ones too (Al(OH)₃, Cr(OH)₃, Zn(OH)₂ etc.).

According to quantity of OH^- bases may be divided into:

One-acidic (NaOH);

Two-acidic (Ca(OH)₂);

Three-acidic (Cr(OH)₃) and so on.

Preparation

1. Interaction of alkaline and alkaline-earth metals and water forming alkalis and free Hydrogen:

2K + 2H₂O = 2KOH + H₂;

Ва + 2Н₂О = Ва(ОН)₂ + Н₂;

2. Direct interaction of alkaline and alkaline-earth metals oxides and water forming the alkalis:

Na₂O + H₂O = 2NaOH;

CaO + H₂O = Ca(OH)₂;

3. Insoluble bases may be prepared by interaction between soluble salts of corresponding metals and alkali solution:

Cu(NO₃)₂ + 2LiOH = Cu(OH)₂¯ + 2LiNO₃;

Fe₂(SO₄)₃ + 3Ca(OH)₂ = 2Fe(OH)₃¯ + 3CaSO₄.

Date: 2015-01-12; view: 1312