Nitrogen

Its electronic formula is 1s²2s²2p³. On the basis of graphic drawing of the external energy level (2s²2p³) the following valency state and oxidation numbers are possible for Nitrogen:

Valency is III (owing to three unpaired electrons of 2p-sublevel). Valency is IV (three - owing to unpaired 2p-electrons, the forth bond - after donor-acceptor mechanism using 2s-electrons). Oxidation numbers are 3-, 2-, 1-, 0, 1+, 2+, 3+, 4+, 5+.

Nitrogen is the typical non-metal, only Fluorine and Oxygen have stronger electronegativity (3,0). The most widespread Nitrogen compounds of different oxidation levels (from 3- to 5+) are shown in Table 17.

Ammonia (NH₃) is colorless gas with purgen odor. In the laboratory heating of NH₄Cl with Calcium hydroxide or any strong alkalis can produce it:

2 NH₄Cl + Ca(OH)₂ 2 NH₃↑+ CaCl₂ + 2 H₂O.

Ammonia can react with water and acids, showing the main properties in the reactions. Practically it does not make NH₄OH hydroxide well dissolved in water (31% at 20⁰C), but reacts with H₂O by means of Hydrogen bond:

Table 17. General characteristic of Nitrogen compounds

NH₃ + H₂O ↔ NH₃·H₂O;

NH₃·H₂O ↔ NH₄OH.

The following important fertilizers are produced by ammonia interaction with acids:

NH₃ + HNO₃ = NH₄NO₃ - Ammonia Nitrate;

2NH₃ + H₂SO₄ = (NH₄)₂SO₄ - Ammonia Sulfate;

NH₃ + H₃PO₄ = NH₄H₂PO₄ - Ammonia dihydrophosphate (ammophos);

2NH₃ + H₃PO₄ = (NH₄)₂HPO₄ - Ammonia hydrophosphate (diammophos).

Nitric oxide (NO) is get by oxidation of Ammonia and it is used as the intermediate product in HNO₃ production:

4 NH₃ + 5 O₂ 4 NO + 6 H₂O

O20 + 4 ® 2 O2-	5 (reduction);
N3- - 5 ® N2+	4 (oxidation).

Nitrogen oxide (III) and nitrous acid

Nitrogen oxide (III) is nitrous acid anhydride:

N₂O₃ + H₂O ↔ 2HNO₂.

As acid oxide it reacts with alkalis:

N₂O₃ + 2NaOH = 2NaNO₂ + H₂O.

Nitrous acid (HNO₂) dissociates with Hydrogen ions formation:

HNO₂ ↔ H⁺ + NO₂^- .

At it’s heating and under the influence of strong acids the process of disproportion takes place:

3HNO₂ ↔ HNO₃ + 2NO + H₂O

N3+ + ® N2+	2 (reduction);
N3+ - 2 ® N5+	1 (oxidation).

Nitrous acid and its salts can be both reducing and oxidizing agents:

2NaNO₂ + 2KI + 2H₂SO₄ = I₂ + 2NO + K₂SO₄ + Na₂SO₄ + 2H₂O

N3+ + 1 ® N2+	2 (reduction);
2I- - 2 ® I20	1 (oxidation).

5KNO₂ + 2KMnO₄ + 3H₂SO₄ = 5KNO₃ + 2MnSO₄+ K₂SO₄ + 3H₂O

Mn7+ + 5 ® Mn2+	2 (reduction);
N3+- - 2 ® N5+	5 (oxidation).

Nitric oxide (V) and nitric acid

Nitric acid and its salts (Nitrates) have the oxidizing properties:

3KNO₃ + 8Al + 5KOH + 2H₂O = 3NH₃ + 8KAlO₂

N5+ + 8 ® N3-	3 (reduction);
Al0 - 3 ® Al3+	8 (oxidation).

Particular feature of nitric acid is in interaction almost with all metals and non-metals, at the same time it oxidizes them. The reduction of N(5+) but not H(1+) as with acids-oxidizing agents always takes place. Generally NO and NO₂ prevail among reduction products. Active metals (Mg, Zn, Ca and others) reduce diluted HNO₃ up to N₂ and NH₄NO₃.

At the same time some N(5+) reduction products can be isolated. However, the equations of such reactions are relative and only one compound (NO₂, NO or N₂, NH₃), formed in quantity, is indicated in the products:

4 Mg + 10HNO₃ (diluted) = 4Mg(NO₃)₂ + NH₄NO₃ + 3H₂O;

Cu + 4HNO₃ (conc) = Cu(NO₃)₂ + 2NO₂ + 2H₂O;

S + 6HNO₃ (conc) = H₂SO₄ + 6NO₂ + 2H₂O;

3P + 5HNO₃ (diluted) + 2H₂O = 3H₃PO₄ + 5NO.

Nitric acid salts - Sodium, Potassium, ammonia, and calcium Nitrates are of great practical value. They are called saltpeters and are used in great quantity as fertililizers.

Date: 2015-01-12; view: 863