Nitrogen and its inorganic compounds

Many industrially important compounds such as: ammonia, nitric acid, propellant, explosives, cyanides and some types of fertilizers contain nitrogen.. It is unreactive at standard temper

I Introduction

Nitrogen is a chemical with symbol N and atomic number 7 The standard atomic weight of Nitrogen is 14 At room temperature, it is a transparent, odorless diatomic gas Nitrogen forms about 80% of Earth’s atmosphere and is the most abundant uncombined element Many industrially important compounds such as: ammonia, nitric acid,

propellant, explosives, cyanides and some types of fertilizers contain nitrogen Moreover, Nitrogen is a nonmetal, its electronegativity is 3.04 It is unreactive at standard temperature and pressure

At atmospheric pressure, molecular nitrogen liquefies and freezes at -210oC Below -237.6oC, nitrogen assumes the cubic crystal allotropic form (called the alpha phase) Liquid nitrogen, a fluid resembling water in appearance, but with 80.8% of the density (the density

of liquid nitrogen at its boiling point is 0.808g/ml), is a common cryogen

II Nitrogen’s properties

In general, nitrogen is un-reactive at standard temperature and pressure because of ít strong triple bond

1 Reaction with H2: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe)

2 Reactions with O2

N2 + O2 → NO↑ (>2000oC)

N2 +O2→NO2↑

3 Metal burns in nitrogen

N2 + Al → 2AlN (Aluminium nitride)

N2 +3 Mg → Mg3N2 (Magnesium nitride)

Metal nitrides are hydrolyzed by water

Mg3N2+ H2O → 3Mg(OH)2+2NH3↑

III Produce nitrogen (N 2 )

1 Industry: produced by fractional distillation of liquid air

2 Laboratory

a) Decay some ammonium salts (NH4+) by heat

NH4NO2 → N2↑+ H2O ( to)

NH4Cr2O7 → N2↑ + Cr2O3 + 4H2O ( to)

NH4NO3 → N2↑+1/2O2↑ + 2H2O

b) 2NH3 + 3O2 → N2↑+ 6H2O (900oC)

2NH3 + 3CuO → N2 + 3Cu + 3H2O (to)

c) Treat an aqueous solution of ammonium chloride(NH4Cl) with sodium nitrite (NaNO2): NH4Cl + NaNO2 → N2↑ + NaCl + 2 H2O

IV Uses of N 2

+) Nitrogen is used to produce ammonia and nitrates are key industrial fertilizers +) Nutrients for all plants have this element

+)The main use of liquid nitrogen is a refrigerant

A.1 Ammonia (NH 3 )

I Ammonia is a colorless gas with a characteristic pungent smell

II Properties

The ammonia molecule has a lone pair electron air, which makes ammonia a base, a proton acceptor

1 NH3 + H2O ⇄ NH4+ + OH

-2 NH3’ reactions with acid:

NH3 + HCl → NH4Cl

2NH3 + H2SO4 → (NH4)2SO4

NH3 + HNO3 → NH4NO3

3 NH3’s reactions with metal cations:

Ag+ + 2NH3 → [Ag(NH3)2]+

Cu2+ + 4NH3 → [Cu(NH3)4]2+

Zn2+ + 4NH3 → [Zn(NH3)4]2+

4 Produce Urea ((NH)2CO): 2NH3+ CO2→ H2N─COONH4

H2N─COONH4 → (NH2)2CO (dehydration)

5 NH3’s displacement reactions: displace 1, 2, or 3 H atom by alkali metals

Na + NH3 → NaNH2 + ½ H2↑ (mole fraction: 1:1)

2Na + NH3 → Na2NH + H2↑ (mole fraction: 2:1)

3Na + NH3 → Na3N + 3/2H2↑ (mole fraction: 3:1)

6 Ammonia’s reactions with metal:

2NH3 + 2Al → 2AlN + 3H2↑ (to)

7 Reduction reactions:

N2 + H2 NH3↑ (.100oC,high pressure , catalyst: Fe)

2NH3 + 3O2 → N2↑+ 6H2O (900oC)

4NH3 + 5O2 → 4NO↑ + 6H2O (250oC, catalyst: Pt)

2NH3 + 3Cl2 → N2↑ + 6HCl

2NH3 + 3CuO → N2↑+ 3Cu↓ + 3H2O (to)

III Produce ammonia

1 Industry: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe)

2 Laboratory

a) Treat an aqueous solution of ammonium salts with alkali liquid

NH4Cl + NaOH → NaCl + NH3↑ + H2O b) Hydrolyze sodium nitride:

Ca3N2 + 6H2O → 3Ca(OH)2 +2 NH3

AlN +3H2O → Al(OH)3↓ + NH3↑

IV.Uses

+) Ammonia is mostly used to produce acid nitric acid, fertilizers

+) People use ammonia to produce hydrazine (N2H4)

+)Solution of NH3 in water is used as a general purpose cleaner for many

surfaces

A.2 Ammonium salts (NH 4 + )

I. Ammonium salts are soluble in water (NH4+) is hydrolyzed in water

II Properties

1 Double displacement reactions:

(NH4)2SO4 + Ba(OH)2 → BaSO4↓ + 2NH3↑+ 2H2O (NH4)2SO3 + 2HCl → 2NH4Cl + SO2↑ + H2O

NH4Cl + AgNO3 → AgCl↓+ NH4NO3

2 Decay ammonium salts by heat

NH4Cl → NH3↑+ Cl2↑ ( to) (NH4)2SO4 → 2NH3↑+ H2SO4 ( to) (NH4)2CO3 → NH3↑+ NH4HCO3 (to)

NH4HCO3 → NH3↑+ CO2↑ + H2O (Sodium bicarbonate, referred to as ‘baking soda’, is primarily used in baking)

III Produce ammonium salts

Treat NH3 with acid liquids

NH3 + HNO3 → NH4NO3

NH3 + H2SO4 → (NH4)2SO4

IV Uses

+) Ammonium salts are used to produce fertilizers, explosives and sodium bicarbonate (NH4HCO3)

+) Ammonium salts are also used to clean metal surfaces

B Nitric acid (HNO3)

I. Nitric acid has a coordinate covalent bond Oxidation number nitrogen

element in nitric acid is +5

Nitric acid is subject to light decomposition and it’s decayed: 4HNO3 → 4NO2↑ +

O2↑ + 2H2O The nitrogen dioxide (NO2) remains dissolved in the nitric acid coloring

it yellow

II Properties

1 Acidity

Nitric acid is a strong acid: HNO3 + H2O → H3O+ + NO3

-Reactions with bases, base anhydrides, salts produce nitrate salts

HNO3 + Fe(OH)3 → Fe(NO3)3 + 3H2O 2HNO3 + CuO → Cu(NO3)2 + H2O

2HNO3 + Na2CO3 → NaNO3 + CO2↑ + H2O

2 HNO3 is a strong oxidizing agent because the nitrogen’s oxidation number is +5

Reactions of nitric acid with almost metals (except gold and platinum) produce metal nitrate salts (M(NO3)n) (n is the highest valence of that metal) and reducing products of HNO3 (such as NO, NO2, N2O, N2, NH3 or NH4NO3), depend on nitric acid’s concentration and metal’s reduction)

Fe + 6HNO3 concentrated → Fe(NO3)3 + 3NO2↑ + 3H2O ( to) 3Cu + 8HNO3 dilute → 3Cu(NO3)2 + 2NO↑ + 4 H2O 8Al + 30HNO3 dilute → 8Al(NO3)3+ 3N2O↑+ 15H2O 4Zn+ 10HNO3 very dilute →4Zn(NO3)2+ NH4NO3+ 3H2O

3 Reactions with some nonmetals such as: S, P, C,… produce acidic oxide with highest oxidation number

S +6HNO3 → H2SO4 + 6NO2↑ + 2H2O 3P + 5HNO3 +2H2O → 3H3PO4 + 5NO↑

C + 4HNO3 → CO2↑ + 4NO2↑ + 2H2O

III.Produce HNO 3

1 Industry:

4NH3 + 5O2 → 4NO↑ + 6H2O ( to)

NO + O2 → NO2

3NO2 + H2O → 2HNO3 + NO↑

OR: 4NO2 + O2 + 2H2O → 4HNO3

2 Laboratory

H2SO4 concentrated + KNO3 → KHSO4 + HNO3 (ĐK PƯ: to)

IV Uses

Nitric acid is mainly for the use of producing TNT, dyes, pharmaceutical products, ect…

Every nitrate salt is soluble in water and The color of this liquid depends on cation Mn+

because ion NO3- is colorless

I Properties of ion NO 3

-1 In acidic environment, ion NO3- has the oxidation like nitric acid 3Cu0 + 8H+ + NO3- → 3Cu2+ + 2NO↑ + 4H2O

2 In alkaline environment, ion NO3- is reduced by Be, Zn, Al and NH3 is the reducing product

4Zn + KNO3 + 7KOH → 4K2ZnO2 + NH3↑ + 2H2O 8Al + 3NaNO3 + 5NaOH + 2H2O → 8NaAlO2 + 3NH3 ↑

3 Decay nitrate salts by heat a) Strong metals (K, Na, Ba, Ca) M(NO3)n → M(NO2)n + n/2O2↑ (to) b) Medium metals ((Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn, Pb, Cu)

2M(NO3)n → M2On + n/2O2↑ + 2nNO2↑

c) Weak metals (Hg, Ag, Pt, Au)

2M(NO3)n → 2M↓ + n/2O2↑ + 2nNO2↑

II Uses

+) Nitrate salts are mainly for the use of producing fertilizers such as: (NH4)2SO4, NH4NO3, (NH2)2CO

+) Potassium nitrate (KNO3) is used to produce gunpowder (contain 75%

KNO3, 10% S và 15% C)

2KNO3 + 3C + S → K2S + N2↑ + 3CO2↑