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What is Atom & Discovery of Electron

 What is Atom & Discovery of Electron

 Stereochemistry PDF Notes

1. Stereo-Chemistry is the branch of the chemistry. Stereochemistry concerned with the 3D arrangement of atoms & molecules and also concerned with the effect of this 

   3D arrangement on chemical reactions. You can download complete stereochemistry PDF notes from our telegram channel @ChemistryNotesInfo

1. What is Stereochemistry ?

2. Stereochemistry is the branch of chemistry. Stereochemistry involves study of the relative spatial arrangement or we can say that 3D (Three-Dimensional) arrangement of atoms that makeup the structure of the molecules. 

What are Stereoisomers ?

Stereoisomers compounds with the same connectivity but different arrangement in the space are known as Stereoisomers.

What are Enantiomers ?

Enantiomers are stereoisomers that have the non-superimposable mirror images. Only property of the enantiomers that differ them are the direction (+ or -) of the optical rotation are known as enantiomers.

What is Diastereomers ?

Diastereomers are the stereoisomers that have not the mirror images but they are different compounds with the different physical properties are known as Diastereomers.

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Link- https://t.me/chemistrynotesinfo/453 

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What will be coming for Plus Two examination chemistry?

 What will be coming for Plus Two examination chemistry?

12th class exams for state boards like Maharashtra and CBSE Board are most likely held in March-April.

All 12th class students, start revising your notes and practicing numerical. If you still not prepared your chemistry notes for coming plus two examination chemistry, then you can use @ChemistryNotesInfo chemistry notes from this website 12th Class  chemistry notes section. 

Dear +2 chemistry students you can also DOWNLOAD PDF of these chemistry notes from our telegram channel. 

Telegram Channel Link To Download PDFs : https://t.me/chemistrynotesinfo

Some Important Plus Two examination chemistry Chapters- 

1. Solid State

2. Solution

3. Electrochemistry

4. Chemical kinetics

5. Surface Chemistry

 6. General Principle and Process of Isolation of the Elements

7. p-block elements

8. d-and f-block elements

9. Coordination compounds

10. Haloalkanes and haloarenes

11. Alcohols, phenols and ethers

12. Aldehydes, ketones and carboxylic acids

13. Amines

14. Biomolecules

15. Polymers

16. Chemistry in Everyday Life

Hydrogen Class 11 Notes

 Hydrogen Class 11th Chemistry Notes

Hydrogen is the first element in the periodic table and is the lightest element. It exists as a diatomic molecule (H₂) and is called dihydrogen. It has one proton and one electron and it has electronic configuration 1s¹. This electronic configuration is responsible for dual nature of hydrogen i.e. hydrogen shows resemblance with alkali metals as well as halogens.

Resemblance of hydrogen with alkali metals

Like alkali metals –

·         Hydrogen exhibits electropositive character i.e. it has tendency to lose electron.

·         The normal valency of hydrogen is 1.

·         Hydrogen forms halides, oxides and sulphides.

·         Hydrogen acts as strong reducing agent.

 

Resemblance of hydrogen with halogens

Like halogens-

• Hydrogen exhibits electronegative character by accepting one electron to complete its valance shell.
• Hydrogen shows same order of ionisation energy (IE₁) as that of halogens.  
• Hydrogen (H₂) is a gas in molecular state similar to F₂ and Cl₂.
• Hydrogen shows -1 oxidation state in its compounds with more electropositive element.

 

POSITION OF HYDROGEN IN THE PERIODIC TABLE

As the hydrogen resembles both the alkali metals and the halogens and also differs from them. Also hydrogen exhibits some unique behavior therefore the position of hydrogen is uncertain and it is placed separately in periodic to table.

ISOTOPES OF HYDROGEN

Hydrogen has three isotopes, protium (₁¹H), deuterium (₁²H) and tritium (₁³H).

            i.            Protium or ordinary hydrogen (₁¹H).

 It is the most abundant isotope of hydrogen (99.985%). Its nucleus has one proton and no neutron (mass no. = 1).

          ii.             Deuterium or heavy hydrogen (₁²H or D).

It is less abundant and is present in heavy water (D₂O). Its nucleus has one proton and one neutron (mass no. = 2).

        iii.            Tritium (₁³H or T)

It is the rarest isotope of hydrogen and is radioactive in nature. Its nucleus has one proton and two neutrons (mass no. = 3).

 

PREPARATION OF DIHYDROGEN (H₂)

Laboratory methods

1.      Action of dilute HCl or H₂SO₄ on granulated zinc.

Zn    +     2HCl     →     ZnCl₂    +    H₂   ↑

 

2.      Action of dilute H₂SO₄ on magnesium ribbon.

Mg    +     H₂SO₄    →     MgSO₄    +    H₂   ↑

 

3.      Action of water on sodium hydride.

NaH    +     H₂O     →     NaOH    +    H₂   ↑

 

4.      By action of KOH of scrap aluminum or silicon. (Uyeno’s method)

2Al    +     2KOH    +     2H₂O     →     2KAlO₂    +    3H₂   ↑

 

Commercial method

1) From water gas (Bosch process)

Water gas (CO + H₂) is mixed with the steam and the gaseous mixture is passed over heated catalytic mixture of ferric oxide (Fe₂O₃) and chromium oxide (Cr₂O₃) at 773K.

H₂     +    CO    +    H₂O      ^{Fe2O3 + Cr2O3 (773K)}  →   CO₂   +   2H₂

  Water gas         Steam

 2) From Steam (Lanes process)

When superheated steam is passed over iron filling heated to 1023 – 1073K hydrogen is formed.

3Fe  +   4H₂O_(steam)      ^{(1023 – 1073)K  (}Fe⁾→   Fe₂O₄   +   4H_2(g)  

                                           

3) Hydrocarbon steam process

Hydrogen is prepared by the action of steam of hydrocarbon at 1270K.

CH₄   +   H₂O       ^1270K  →   CO   +   3H₂

 

4) By electrolysis of water

Electrolysis of acidified water using platinum electrodes gives dihydrogen. Here dihydrogen is librated at the cathode while dioxygen is librated at anode.

 

CHEMICAL PROPERTIES OF DIHYDROGEN

1) Dihydrogen reacts with halogens (X₂) to give hydrogen halide (HX).

    H₂   +   X₂    →   2HX    ( X = F, Cl, Br, I )

 

2) Dihydrogen reacts with dioxygen to forms water. This reactions is highly exothermic.

    2H₂   +   O₂      ^{catalyst or heating}  →   2H₂O . ΔH = -285.9 KJ.mol^-1

 

3) With dinitrogen dihydrogen forms ammonia. This process is coiled Hober process of    

    manufacture of ammonia.         

    3H₂   +   N₂     ^{673K, Fe catalyst, 200atm}  →   2NH₃

 

4) Dihydrogen combines with many metals at high temperature to yield the corresponding                             hydrides                                                                                                                                                                                                                                                                                                 

   2Na  +  H₂   →  2NaH    (sodium hydride)

 

5) It acts as reducing agent and thus reduces certain oxides of metals.

    ZnO   +   H₂   →   Zn   +   H₂O

    Fe₂O₄   +   4H₂   →   3Fe   +   4H₂O

6) Hydrogenation of vegetable oils using nickel as catalyst gives edible facts (margarine and Vanaspati ghee)

    Vegetable oil   +   H₂      ^{Finely divided Ni, 450K, 8-10atm}  →  Solid fat

 

USES OF DIHYDROGEN

·         Dihydrogen is used in the preparation of ammonia by Haber’s process.

·         It is used in the hydrogenation of vegetable oils.

·         It is used for the manufacture of metal hydrides.

·         It is used as rocket fuel in space research.

·         Dihydrogen is used in fuel cell for generating electrical energy.

·         It is used in the atomic hydrogen torch and oxy hydrogen torches for cutting and welding.

 

HYDRIDES

The binary compounds of hydrogen with other elements are called hydrides. These hydrides have the formula EH_x or E_mH_n (E = Element). These are classified into three types.

a) Ionic or saline hydrides

b) Covalent or molecular hydrides

c) Metallic or nonstoichiometric or interstitial hydrides

 

a) Ionic or saline hydrides

These are formed by the combination of hydrogen with metals which have low electro negativity values and are electropositive with respect to hydrogen. These includes elements of S block element. Ionic hydrides are prepared by the direct combination of metals.

e.g. LiH, KH, CaH₂, MgH₂ etc.

 

b) Covalent or molecular hydrides

These hydrides are formed by the combination of elements of comparatively higher electro –negativity as p-block element. The bonds formed are mostly covalent in character. Covalent hydrides are generally volatile.

e.g. H₂O, CH₄, NH₃, HF etc.

 

c) Metallic or nonstoichiometric or interstitial hydrides

Metallic hydrides are formed by many d - block and f - block  elements. Elements of group 7, 8, 9 of d – block do not form hydrides and this is referred as hydride gap. Metallic hydrides are non – stoichiometric and show electric conductance. In these hydrides, hydrogen occupies interstices in the metal lattice producing distortion without any change in its type. Therefore, they are termed as interstitial hydrides.

e.g. SCH₂, TiH₂, VH, ZrH₂

  

WATER (H₂O)

Water is essential to all forms of life. It is most common, abundant and easily obtainable of all chemical compounds. It is regarded as universal solvent. Water (H₂O) is hydride of oxygen. In nature, water exist in three physical states, water (liquid), Ice (Solid) and water vapour (gas).

 

Structure of water

Water molecule is a bent molecule with bond angle of 104.5ᵒ and O-H bond length is 95.7pm.

Structure of Ice

Ice is the solid form of water. It has a highly ordered three dimensional hydrogen bonded structure. In ice each oxygen atom is surrounded tetrahedrally by four other hydrogen atoms at a distance of 276pm. The strength of hydrogen bonding in ice is more than liquid water. There is empty space in crystal of ice due to hydrogen bonding. This makes density of ice lower than liquid water, hence ice floats on water.

Chemical properties of water

1) Dissociation of water

Water dissociates into its ion.

H₂O   +    H₂O      →       H₃O⁺       +        OH^-

                                 Hydronium ion

 

2) Amphoteric nature

Water has the ability to act as on acid as well as base. Such kind of behavior is known as amphoteric nature.

 H₂O     +      NH₃      →       OH^-         +        NH₄⁺

 H₂O     +      HCl      →       H₃O⁺       +        Cl^-

                                   

 

3) Oxidizing and reducing nature

Water can act both as an oxidizing and reducing agent in its chemical reactions. With active metals water behaves as an oxidizing agent while with highly electronegative element, it acts as a reducing agent.

2Na    +    2H₂O    →    2NaOH    +    H₂

        Oxidizing agent

2F₂    +    2H₂O    →    4HF    +    O₂

        Reducing agent

 

4) Formation of Hydrates

Water has strong ability to form compounds with some metal salts known as hydrates. This hydrates can be classified into three types:

i) Coordinated water

[Cr(H₂O)₆]³⁺3Cl^-

ii) Interstitial water

BaCl₂.2H₂O

iii) Hydrogen – bonded water

[Cu(H₂O)₄]²⁺SO₄^2-.H₂O     in

CuSO₄.5H₂O

 

HEAVY WATER

Heavy water is deuterium oxide (D₂O). It was discovered by Urey in 1932. The reaction of D₂O are slightly slower than H₂O. Ordinary water contains one part of heavy water in 6000 part of it. It is used as a moderator in nuclear reactors. It is used as tracer compound in determining the mechanism of many organic reactions.

 

HARD AND SOFT WATER

Natural water contains dissolved salts. Depending upon its behavior towards soap solution, water may be classified as hard water and soft water.

a) Soft water : 

Water which produces lather with soap solution readily is called soft water. For example : distilled water, rain water, and demineralized  water.

 

b) Hard water : 

Water which does not produces lather with soap solution readily is called hard water. For example : sea water, river water, well water and tap water.

The hardness of water is due to the presence of the bicarbonates, chlorides and sulphates of calcium and magnesium.

 

Isotopic varieties of water

Ordinary water contains 18 different kinds of water. Such as variety is possible due to the different isotopic forms of hydrogen and oxygen. Hydrogen has three isotopes H(protium), D(Deutrium), T(tritium) and oxygen also has three isotopes ¹⁶O, ¹⁷O, ¹⁸O. These isotopes of hydrogen and oxygen combine to give 18 different kinds of water from which H₂O is most abundant.

 

 

HYDROGEN PROXIDE (H₂O₂)

Hydrogen peroxide was discovered by Thenard in 1818. It is an important chemical used in pollution control treatment of domestic and industrial effluents.

 

Preparation of H₂O₂

1) In laboratory H₂O₂ is prepared by acidifying barium peroxide and removing excess water by evaporation under reduced pressure.

BaO₂.8H₂O   +   H₂SO₄    →   BaSO₄   +    H₂O₂   +    8H₂O

 

2) By the action of dilute acid on sodium peroxide (Merck’s method)

Na₂O₂   +   H₂SO₄    →   NaSO₄   +    H₂O₂

 

3) By bubbling CO₂ through a paste of BaO₂

BaO₂   +    H₂O   +   CO₂    →   BaCO₃ ↓   +    H₂O₂

 

4) By the action of phosphoric acid on BaO₂

3BaO₂    +   2H₃PO₄    →   Ba₃(PO₄)₂ ↓   +    3H₂O₂  

 

5) Industrially H₂O₂ is prepared by the auto – oxidation of 2 – Ethyl anthraquinol.

      2-ethyl anthraquinol     O₂ (air) (H₂/Pd) →   2-ethyl anthraquinol    +   H₂O₂

 

Structure of  H₂O₂

It is non–planar open book (Skew) structure. The bond length and bond angle are slightly different in gas and solid phase due to hydrogen bonding. Structure of  H2O2 HYDROGEN PROXIDE.

Chemical Properties of H₂O₂

1) It decomposes rapidly on heating in presence of finely divided metals, such as Ca, Fe, Cu, Au, Ag, Pt, MnO₂, Carbon, dust, light, etc.

H₂O₂   +   H₂O₂    →    2H₂O    +    O₂   (ΔH = -196KJ)

 

2) It acts as an oxidizing as well as reducing agent in both acidic and alkaline or basic medium. Some example are given below

i) Oxidizing action in acidic medium

PbS   +   4H₂O₂    →    PbSO₄   +   4H₂O

ii) Reducing action in acidic medium

HOCl    +   H₂O₂    →    H₃O⁺   +    Cl^-    +   O₂

iii) Oxidizing action in alkaline medium

Mn²⁺   +   H₂O₂   →   2Fe³⁺   +    2OH^-

iv) Reducing action in alkaline medium

Cl₂   +   H₂O₂   +    2OH^-   →   2Cl^-   +    2H₂O    +    O₂

 

3) Hydrogen peroxide acts as a bleaching agents due to the release of nascent oxygen.

H₂O₂     →     H₂O     +     O

 

4) Hydrogen peroxide undergoes addition reaction with alkenes to form glycols.

Uses of H₂O₂

·         It is widely used in environmental chemistry.

·         It is used as a antiseptic and is sold in the market as perhydrol.

·         It is used in daily life as a hair bleach and as mild disinfectant.

·         It is used as a bleaching agent and to manufacture chemicals like sodium perborate and percarbonate.

 

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