Nitrogen & Its Compounds

I. Dinitrogen

Nitrogen is a very important part of our atmosphere. It forms 78% of our atmosphere by volume and 75% by mass.

Preparation : We have two types of productions of Nitrogen:

Commercial production : The commercial production of Nitrogen is done by the liquifaction and fractional distillation of air.

Lab production : In lab Nitrogen can be produced by several methods-

I. When aqueous solution of ammonium chloride is treated with sodium nitrite.

NH4Cl(aq)+NaNO2(aq)→ N2(g) + 2H2O(l) + NaCl(aq)

II. Dinitrogen can also be obtained by the thermal decomposition of ammonium dicromate.

(NH4)2Cr2O7 →N2(g) + 2H2O(l) + Cr2O3

III. Thermal decomposition of sodium or barium azide also gives dinitrogen. Nitrogen obtained by this method is very pure.

Ba(N3)2 → Ba + 3N2

II. Ammonia()

Ammonia was detected by Priestley in 1774. It is generally formed by the bacterial decomposition of nitrogenous matter found in plants and animals. We can find it in a very less amount in air and soil.

Commercial production: Ammonia is produced by Haber’s process commercially. In this process we prepare a setup with following optimum conditions:

1. Pressure :200 × 105 Pa or 200 atm(Approx), 2. Temperature : About 700 K & 3. Catalyst : Iron oxide with small amount of K2O & Al2O3.

IMG_20180627_121911.jpg

Under these conditions ammonia is produced by the reaction : N2(g) + 3H2(g) → 2NH3(g)

The catalyst is used to increase the production rate of NH3.

III. Oxides of Nitrogen

Nitrogen reacts with oxygen to form different oxides with different oxidation state

1. N2O -Dinitrogen Oxide or Nitrous Oxide or Laughing Gas:

Oxidation state of Nitrogen: 1

Preparation: It can be produced by heating ammonium nitrate.

NH4NO3 N2O + 2H2O

Structure:

Properties : 1. Nitrous oxide is a colourless gas.

2. It is a has with sweet taste and pleasant odour.

3. It can create laughter when inhaling in a sufficient amount due to which it is called laughing gas.

4. It is soluble in cold water but not in hot water.

5. Nitrous oxide is heavier than air.

Uses : 1. As propellant, 2. As anaesthetic in minor surgical operations with oxygen

II. HNO3-Nitric Acid

Commercial Preparation(Ostwald Process):

The mixture of ammonia and air when passed over platinum gauze catalyst at 7500C-9000C, then ammonia is oxidised to nitric acid.

4NH3+5O2 – 4NO + 6H2O

By oxidising, the nitric oxide is converted to nitrogen dioxide.

2NO + O2 – 2 NO2

When nitrogen dioxide is cooled and absorbed in water, nitric acid is obtained.

3NO2 + H2O – 2HNO3 + NO

Lab Preparation: In the laboratory, nitric acid is formed by heating the mixture of KNO3 or NaNO3 and concentrated H2SO4 in a glass retort.

KNO3 + H2SO4 – KHSO4 + HNO3

NaNO3 + H2SO4 – NaHSO4 + HNO3

The Nitrogen Family

Elements in 15th group are known as ‘The Nitrogen Family’. The family includes the following elements:

Elements

Symbol State

Metallic Properties

Nitrogen

N Gas Non-metal
Phosphorus P Solid

Non-metal

Arsenic

As Solid Metalloid
Antimony Sb Solid

Metalloid

Bismuth

Bi Solid Metal

Occcurence : Nitrogen – Nitrogen is found in the molecular form in the atmosphere. It comprises 75% by mass and 78% by volume of the atmosphere. It is also found in Earth’s crust in the form of Chile Saltpetre(Sodium Nitrate : NaNO3) and Indian Saltpetre(Potassium Nitrate-KNO3). In the form of protein, Nitrogen is also available in plants and animals.

Phosphorus : Minerals of the apatite family are main source of phosphorus as flourapatite : Ca9(PO4)6.CaX2 where X =F, Cl and Br. In the animal and plant matter nitrogen is an essential component. It is also found in bones of animals. As phosphoproteins it is available in milk and eggs.

Arsenic, Antimony & Bismuth : They are found in sulphide minerals.

Properties of 15th group elements :

Atomic properties :

● Electronic configuration : The electronic configuration of the outermost shell is ns2np3. Due to half filled p orbital these elements are quite stable.

Atomic & ionic radio :

Reactivity towards oxygen : Group 15 elements form oxides by reacting with oxygen of the form E2O3, E2O4 and E2O5 .Ex: N2O3, N2O4, P2O5, As2O5 etc.

Key Points : 1. Among oxides the acidic nature increases with increase in the oxidation state.

2. The acidic nature also increases with increase in the percentage of oxygen.

3. In the group, the acidic nature decrease with increase in atomic number due to increase in the metallic character.

E2O3 Type Oxides of

Nature

Nitrogen & Phosphorus

Purely acidic

Arsenic & Antimony

Amphoteric

Bismuth

Basic

4. The stability of oxides decreases down the group.

Reactivity towards Hydrogen : Group 15 elements react with Hydrogen to form hydrides of the form EH3. Ex : NH3 (Ammonia), PH3 (Phosphine), BiH3 (Bismuthine) etc.

Key Points : 1. The thermal stability decreases down the group because the tendency to form covalent bond decreases as the size of atoms increases which leads to increase in the metallic character.

Classification of Crystalline Solids

In this topic, we have to discuss the types of crystalline solids. Crystalline solids are classified into four categories as follows:

1. Molecular solids: Solids whose constituent particles are molecules are called molecular solids.

Molecular solids are of three types:

I. Non-polar molecular solids: A solid in which the constituent particles are held by weak dispersion forces or London forces are called non-polar molecular solids.

Ex: H2, O2, N2, Noble gases like He, Ne, Ar, Kr etc

II. Polar molecular solids: A solid in which the constituent particles are held by dipole-dipole forces is called a polar solid.

Ex: HCl, NH3, SO2 etc

III. Hydrogen bonded molecular solids: A solid in which the constituent particles are held by Hydrogen bond is called a hydrogen bonded molecular solids.

Ex: Ice, HF etc

2. Covalent or network solids: A solid in which the constituent particles form a huge network of very strong covalent bonds is called a covalent or network solid.

Ex: Diamond, Graphite, Silica, Silicon Carbide etc.

3. Ionic solids: A solid whose constituent particles are ions is called an ionic solid.

Ex: NaCl, MgCl2 etc

4. Metallic solids: A solid whose constituent particles are atoms of a metal is called a metallic solid.

Ex: Fe, Cu, Zn etc.

Trigonometric Equations

Trigonometric equation: An equation having trigonometric functions is called a trigonometric equation.

Ex : sin θ = 1

sin θ + cos θ =1

tan θ = 1

Trigonometric identity : A trigonometric identity is also an equation which gets satisfied by any value of the unknown quantity.

Ex : sin2θ + cos2θ=1

Key Point: A trigonometric equation is satisfied by finite or infinite specific values of the unknown quantity not by any value of the unknown quantity.

Solution of a trigonometric equation: There are two types of solutions of a trigonometric equation:

I. Principal solution: A solution in which the values of the unknown quantity belong to the interval [0,2π] is called a principal solution.

II. General solution: A solution in which there are infinite values of the unknown quantity is called a general solution.

Important results :

I. sin θ = 0 ⇒ θ = nπ           II. cos θ = 0 ⇒ θ = (2n+1)π/2             III. tan θ = 0 ⇒ θ = nπ

Amines

When one or more hydrogen atoms of ammonia molecule are replaced by alkyl or aryl group amines are formed. These are also called derivatives of ammonia.

Classification of amines: Amines can be classified into three categories:

I.Primary amines: If one hydrogen atom is replaced by R or Ar, we get a primary amine.

II.Secondary amines: If two hydrogen atoms are replaced by alkyl or aryl group we get a secondary amine.

III.Tertiary amines: If three hydrogen atoms are replaced by alkyl or aryl group, we get a tertiary amine.

Alcohols, Phenols & Ethers

Intro: When a hydrogen atom from a hydrocarbon whether aliphatic or aromatic is replaced by -OH group alcohols and phenols are formed.

Ex:

But, when a hydrogen atom from a hydrocarbon whether aliphatic or aromatic is replaced by alkoxy or aryloxy group(R-O/Ar-O) alcohols and phenols are formed.

Ex:

Classification

Haloalkanes & Haloarenes

Intro: When hydrogen atoms are replaced by halogens in hydrocarbons whether aliphatic or aromatic, alkyl halide (haloalkanes) and aryl halide(haloarenes) are formed.

Difference between haloalkanes and haloarenes:

1.In haloalkanes, halogens are attached to sp3 hybridised carbon atoms of alkyl group.

However, in haloarenes halogens are attached to sp2 hybridised carbon atoms of aryl group.

Coordination Compounds

Compounds in which transition metals make several anions or neutral molecules are called coordination compounds. Ex: Chlorofyll, haemoglobin, vitamin B-12 etc.

Werner’s theory for coordination compounds: In 1898, a swiss chemist propounded his theory of coordination compounds. The main points of this theory are as follows:

1. Metals show two types of linkages or valences- primary and secondary in coordination compounds.

2. The primary valences are normally ionisable and are satisfied by anions(negative ions).

3. The secondary valences are nonionisable.

4. The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers.

Isomerism in coordination compounds: Compounds having same molecular formula but different structures are called and this phenomenon is called isomerism.

Coordination compounds show two types isomerism: 1. Structural isomerism and 2. Stereo isomerism

I.Structural isomerism : Isomerism due the difference in the structures of compounds is called structural isomerism. This isomerism is of four types:

2. Stereo or space isomerism : The isomerism due to the different relative positions of the ligands is known as stereo isomerism. This isomerism is of two types :

I. Geometrical isomerism : The isomerism in which isomers differ in the spatial distribution of atoms or groups about the central atom is known as geometrical isomerism. It is also known as cis-trans isomerism.

Ex :

Hydrocarbon

Definition: The compounds which are made up of carbon and hydrogen are called hydrocarbons.

Types of hydrocarbons: Hydrocarbons are of mainly three types:

I. Saturated, II. Unsaturated and III. Aromatic

I. Saturated hydrocarbons: Such hydrocarbons which are formed by C-C single bond or C-H single bond are called saturated hydrocarbons.

II. Unsaturated hydrocarbons: Such hydrocarbons which are formed by C-C double or triple or both bonds are called unsaturated hydrocarbons.

Metallurgy

Metals are very important for us. Many useful things like utensils, different types of tools, vehicles, tanks etc are made up of metals. But, metals are not easily available. Only a few metals are found in free state. Maximum metals are found in the combined form i.e. mineral in earth’s crust.

Ore : A mineral from which the extraction of a metal is feasible and economical is called an ore.

Abundance of metals : Aluminium is the most abundant element among metals. It is 8.3% by weight in earth’s crust. The main ores of some important metals are as follows:

Metal

Ores

Composition

Aluminium

Bauxite

Kaolinite

AlOx(OH)3-2x Where 0<x<1 </x<1

Al(OH)4.Si2O5

 

Iron

Haematite

Magnetite

Siderite

Iron pyrite

Fe2O3

Fe3O4

FeCO3

FeS2

Copper

Copper pyrite

Malachite

Cuprite

Copper Glance

CuFeS2

CuCO3 . Cu(OH)2

Cu2O

Cu2S

Zinc

Zinc Blende or Sphalerite

Calamine

Zincite

ZnS

ZnCO3

ZnO

Metallurgy : The whole technological and scientific process of the isolation of a metal from its ore is called metallurgy.

Gangue : An ore contains several unwanted impurities with a metal which are called gangue.

Concentration of ores : The process of removing guange from an ore is called the concentration of ore.

There are different methods of the concentration of the ores of different metals. Some of them are as follows :

1. Hydraulic washing : This method is based on the difference in specific gravities of the ore and the gangue particles.

Procedure : In this method, water with high speed is drawn on ore particles due to which lighter gangue particles flow with water and ore particles are left behind.

2. Magnetic separation method : This method is based on the differences in magnetic properties of the ore components.

Procedure : In this method, the powdered ore is placed over a conveyer belt which passes over a magnetic roller. The ore particles fall near the roller due to the attraction and gangue particles fall far from the roller.

Refining : Metals obtained from the extraction process are not pure. They still have some impurities. The process of removing these impurities is called refining. For different metals, different refining processes are used.

I. Distillation(Zn/Hg) : The metals with low boiling points are refined by distillation. In this method, the metal with impurities is heated, due to the low boiling point metal vaporizes and it is collected in a flask and impurities are left behind.

II. Liquation(Sn) : This method is suitable for metals having low melting points. In this method, the metal with impurities is heated, due to the low melting point metal vaporizes and it is collected in a flask and impurities are left behind due to their high melting point.

 

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