MHRN P BLOCK Group 15 Nitrogen Family.pdf

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1. P BLOCK

2. GROUP 15
Nitrogen family
Allotropy :-

8. General Trend and Chemical Properties:-
All these oxides are generally covalent and acidic. Sb O is amphoteric
and Bi O is basic.
Acidic nature decreases from the oxide of nitrogen to that of bismuth.
The order of Boiling point : PH AsH NH SbH BiH
The order of Melting point : PH AsH SbH NH BiH
(iv) In case of nitrogen, only NF is known to be stable.

9. These elements react with metals to form their binary compounds exhibiting –3
oxidation state

10. COMPOUNDS OF NITROGEN & PHOSPHOROUS
DINITROGEN :-
From liquified air by fractional distillation (bp of N is –196 C)
It can be obtained by making ammonium nitrite and then warming it
Lab preparation:-
commercial preparation :-

11. Physical properties :-
Ammonia :-
Preparation :-
Laboratory method
By the action of any base or alkali on any ammonium salt

12. Industrial methods
(iii)From destructive distillation of coal.
When coal is heated at a high temperature in an iron retort and the distillate
is bubbles in water, three substances are obtained :
(a) Tarry black pitch,
(b) Liquor ammonia
(c) Coal gas
(concentrated solution of ammonia and ammonium salts)
Physical and chemical properties :-
Ammonia is a colourless gas with a pungent odour.
In the solid and liquid states, it is associated through hydrogen bonds, that
accounts for its higher melting and boiling points than expected.
Ammonia gas is highly soluble in water. Its aqueous solution is weakly basic due
to the formation of OH ions.
NH act as lewis base due to the presence of lone pair

13. As a weak Lewis acid, it precipitates hydroxide of many metals from their salt solution
Thermal dicompostion of ammonium salts :
Ammonium salts decompose quite readily on heating. If the anion is not
particularly oxidising
When NH3 gas is passed into the colourless solution of Nessler’s reagent a brown
precipitate or coloration is formed. This is a test for NH gas.

14. USES OF NH3 :

1.Used as a refrigeration fluid.

2.For the production of ammonium fertilizers such as
ammonium sulphate, ammonium phosphate, ammonium nitrate,
urea etc.

3.For removing grease because NH4 OH dissolves grease.

4.For manufacture of HNO3 by the Ostwald process.

5.As a laboratory reagent.

6.In the production of artificial rayon, silk, nylon etc.

18. Preparation:-
Physical and chemical properties
It is a colourless liquid.
In the gaseous state, HNO exists as a planar molecule.
In aqueous solution, HNO behaves as a strong acid giving hydronium and
nitrate ions.
Concentrated nitric acid is a strong oxidising agent and attacks most metals
except noble metals such as gold and platinum.

19. Some metals (e.g. Cr, Al) do not dissolve in concentrated nitric acid because
of the formation of a passive film of oxide on the surface.
Concentrated nitric acid also oxidises non–metals and their compounds.
Brown Ring Test :-
It depends on the ability of Fe2+ to reduce nitrates to nitric oxide, which reacts
with Fe2+ to form a brown coloured complex.
The test is usually carried out by adding dilute ferrous sulphate
solution to an aqueous solution containing nitrate ion, and then carefully adding
concentrated sulphuric acid along the sides of the test tube. A brown ring at the
interface between the solution and sulphuric acid layers indicate the presence
of nitrate ion in solution.
USES OF HNO3 :

(i) The major use of nitric acid is in the manufacture of ammonium nitrate for
fertilizers and other nitrates for use in explosives and pyrotechnics.

(ii) It is also used for the preparation of nitroglycerin, trinitrotoluene and other
organic nitro compounds.

(iii) Other major uses are in the pickling of stainless steel, etching of metals and
as an oxidiser in rocket fuels

20. It is obtained by reduction of calcium phosphate with C in an electric furnace
at 1400-1500°C
PHOSPHOROUS :-
In the laboratory, it is prepared by heating white phosphorus with concentrated
NaOH solution in an inert atmosphere of CO2 .
PROPERTIES :
Colourless gas
Slightly garlic or rotten fish smell
Highly poisonous.
It explodes in contact with traces of oxidising agents like HNO3 , Cl2 and
Br2 vapours.
It is slightly soluble in water but soluble in CS2 and other organic solvents.
The solution of PH3 in water decomposes in presence of light giving red
phosphorus and H2 .

21. When absorbed in copper sulphate or mercuric chloride,
Phosphine is weakly basic
The spontaneous combustion of phosphine is technically used in Holme’s signals.
It is a white powder
Acidic in nature
Anhydride of orthophosphoric acid.
Dissolves in water with hissing sound forming metaphosphoric acid and finally
orthophosphoric acid.

22. Dehydrates concentrated H SO and concentrated HNO to SO and N O respectively.