As nh4oh is a weak base|foundation|.
Salts of ammonium are stable|firm| under ordinary|usual| conditions, but at heating are decomposed. Nature of the final|end| products product of thermal decomposition of ammonium salts is mainly determined by the properties|virtue| of anion|.
If an acid residue is a strong oxidant |remainder|, ammonium nitrogen is oxidized: in such reaction ammonium nitrogen gives|return| 4 electrons to nitrate anion nitrogen which|what| is|appear| an oxidant. On the other hand|on other hand|, this reaction is an example of intramolecular disproportionation|.
Other examples are:
NH4NO2 = N2 + 2H2O
(NH4)2Cr2O7 = Cr2O3 + N2 + 4H2O
3(NH4)2SO4 = N2 + 3SO2 + 6H2O + 4NH3
If an acid is|appear| not an oxidant, the type|nature| of decomposition depends on its volatility at temperature of decomposition:
1. From the salts of non-volatile acids is eliminated only NH3:
(NH4)3РO4 = 3NH3 + H3РO4
2. If an acid is volatile|flying| (for example HCl)
NH4Cl = NH3 + HCl
at cooling it again forms an initial|output| salt and process of decomposition looks like sublimation of salt.
In liquid|rare,thin| ammonia exist dimers (NH3)2 which|what| are able to|by| selfdissociate. However, this process is |it|extraordinarily moved to the left (at -50оС):
(NH3)2 = NH4+ + NH2- К = 2.10-33
2. reactions of substitution. The reactions of hydrogen substitution of ammonia are less characteristic|character,typical|, than the reactions of addition. They proceed at high temperatures. At substitution of one hydrogen in NH3 it forms amides of metals MeNH2, at substituting of two atoms of hydrogen –imides of | metals Me2NH, at substituting of three atoms of hydrogen – nitrides of| metals.
Amides. Dry ammonia interacts with metals (in fusions):
2
+
2Na = 2NaNH2
+
= -145 kJmol NaNH2-
amide|
Thus, here hydrogen of NH3 lowers its oxidation state while NH3 acts as an oxidant. On the other hand|on other hand|, this reveals| the acidic nature of NH3|virtue|. Amides of metals are|appear| typical|model| salts of NH3, which|what| correspond to its|its| acidic function. Acid nature of NH3 is expressed very poorly, the constant of acid ionization extraordinary low (рКа 35), that is why|that is why| salts of NH3 as acids in water hydrolyse| completely:
NaNH2 + H2O = NaOH + NH3
Imides. Dry ammonia interacts with metals (at fusion):
NH3 + 2Li = Li2NH + H2; Li2NH- lithium imide
Imides also can be prepared|received| by careful heating of amides|:
2LiNH2 = LiNH + NH3
Imides also correspond to the acidic function of ammonia.
Nitrides. At annealing| of solid Al in the atmosphere of NH3 occurs a reaction:
2Al + 2NH3 = 2AlN + 3H2
this process of preparation of nitride| coating films is called nitridation|.
Nitrides of metals, unlike halides or| sulfides, are|appear| not salts, as they do not correspond to any|some,any| acids. They are formed at high temperatures:
3Mg + N2 = Mg3N2
2B + N2 = 2BN
Properties|virtue| of nitrides| more or less appropriately change according periods and groups of the periodic system. For example, in small periods there is observed a transition from| basic|main| nitrides |to|by| acidic ones:
Na3N Mg3N2 AlN Si3N4 P3N5 S4N4 Cl3N
basic|main| amphoteric| acidic
Nitrides are classified so: ionic (Li3N), covalent| (NH3) and “inclusion”|inclusion| (Fe4N, Fe3N). Nitrides of| s-elements have mostly ionic type of bonds|truss|, oxidation state of nitrogen there is -3. These nitrides| are crystalline compounds. They are chemically active, easily react with water:
Mg3N2 + 6H2O = 3Mg(OH)2 + 2NH3
Nitrides BN, AlN, Si3N4 are polymeric compounds with high temperatures of melting (2000-3000оС), they are dielectrics or semiconductors.
Nitrides of d-metals (Fe4N, Fe3N, Ni3N) are compounds|halving,compound,junction,joint,coupling| with metallic bond, they have metallic (electronic) conductivity. They are products of squeezing of atoms of nitrogen into the holes of crystalline grate of metals. Filling of these empty space account for material strengthening, those nitrides are remarkably hard |, refractory|that is why|, chemically inactive, not reacting with water, only slowly|sluggishly| reacting with acids. The oxidation state of elements in them is accepted as equal to|equal| zero.
It is obvious, that from the covalent| nitrides| a greatest practical value|importance,meaning| has nitride| of hydrogen of NH3- ammonia. Next to derivatives of metals are known the products of substituting of hydrogens of ammonia on a halogen, for example chlorous nitrogen of NСl3, which|what| forms as yellow oily drops obtained at|receive|action act|act| action of Cl2 on the concentrated solution of NH4Cl:
NH4Cl + 3Cl2 = NCl3 + 4HCl (1HCl + 3HCl)
NСl3 is very unstable, at heating to|by| 90оС or at slight blow|kick| it decomposes with an explosion on elements. In water NСl3 is not dissolved, but slowly|sluggishly| hydrolysed|it|:
NCl3 + 3H2O = NH3 + 3HOCl
3. Reactions of oxidation. The oxidation state of nitrogen (-3) in NH3 is|appear| lowest, however |virtue| its reduction |its| activity is expressed very poorly: NH3 does not burn|burning| in air, it does not react in solutions with most oxidants, for example with compounds|halving,compound,junction,joint,coupling| of Cr(VI). It is explained with the fact that NH3 and ion of NH4+ are comparatively stable molecules|firm|.
However NH3 normally burns|burning| in the atmosphere of oxygen:
4NH3 + 3O2 = 2N2 + 6H2O
and|but| in the presence of catalysts in the air:
4NH3 + 5O2 = 4NO + 6H2O (basic|main| process of HNO3production)
Cl2 and Br2 oxidize ammonia vigorously:
2NH3 + 3Cl2 = N2 + 6HCl
(this reaction proceeds also in solutions).
Ammonia interestingly|curiously| reacts with J2.Thus forms extraordinarily unstable compound NI3, which|what| |appear|, when it is dried up, violently explodes from| a least touch («chemical inviolability»).
NH3 can reduce oxides|oxide|:
2NH3 + 3CuO = 3Cu + N2 + 3H2O
On the whole|all in all| the properties|virtue| of NH3 can be presented in such a chart:
Hydrazine, N2H4. It is a colourless toxic liquid which|what| easily evaporates (tboiling = 113,50С), it has high dielectric permeability ( = 52 at 25оС), it is polar (=1.85 D).
The structure|building| of N2H4 is similar|like| to|by| H2O2 (the so-called|so called| goch-configuration|shape|):
Trans- goch-
More symmetric trans-form|shape| does not answer reality, as N2H4 has high dipole moment (1.85D), greater than in water, which|what| can not be demonstrated|shown,turned,displayed| at the symmetric trans form|shape|.
Preparation. In laboratory:
2NH3 + NaClO = N2H4 + NaCl + H2O
Chemical properties|virtue|. Chemical properties|virtue| of N2H4 look a great deal similar to those of ammonia. In its|its| aqueous|aquatic,water| solutions also exist hydrogen bonds|truss|. Basic|main| properties|virtue| of N2H4 are related|tied| to the mobility of electronic pair|couple| on the atom of nitrogen. Being a donor of two electronic pair|couple|, in an acidic medium|Wednesday| hydrazine adds protons:
NH2NH2 + H+ = NH3+NH2 К1 = 8.5.10-7
NH3+NH2 + H+ = NH3+NH3+ К2 = 8.5.10-15
As a result salts of |hydrazine are known as follows |that is why|:
N2H4 + HCl = [N2H5]Cl = N2H4.HСl
N2H4 + 2HCl = [N2H6]2+Cl2
Cation [N2H6]2+ is stable|firm| only at large|great,big| excess|overabundance| of strong acid, in other case it is|its| completely hydrolysed:
NH3NH32+ + H2O NH3NH2+ + H3O+
The atom of nitrogen in N2H4 is characterized|described| by Red-Ox duality:
demonstrates |virtue| reductive properties;
N2H4 + O2 = N2 + 2H2O
3N2H4 = N2 + 4NH3
N2H4 + 2I2 = N2 + 4HI
N2H4 + 2Cl2 = N2 + 4HCl
5N2H4 + 4KMnO4 + 6H2SO4 = 5N2 + 4MnSO4 + 2K2SO4 + 16H2O
much weaker are expressed its oxidizing properties|virtue|
N2H4 + 2H+ = 2NH3
(Zn+HCl)
Hydroxylamine, NH2OH. It is a solid white compound, m.p. = 33 oС. Thermally unstable; at higher than 100оС it explodes. Its|its| aqueous solutions are more stable|firm|.
Preparation. Electrolysis on cathode at reduction of HNO3 solution by atomic hydrogen gives NH2OH
HNO3 + 6H+ + 6е = NH2OH + 2H2O
An atom of nitrogen in NH2OH is a donor of electronic pair|couple|, that is why|that is why| NH2OH forms a drogen bond. Like NH3 and N2H4 in water of NH2OH is a weak base|foundation|. In the series NH3 (К = 10-5) N2H4 (К = 10-6) NH2OH (К = 10-8) basic|main| properties|virtue| diminish.
With acids NH2OH forms salts according to reaction of addition type:
NH2OH + HCl = [NH3OH]Cl