CH-4 (CARBON AND ITS COMPOUNDS) Class-10 | NCERT Topper Notes

Chapter-4
Carbon and its Compounds

Introduction :

• The element carbon is non-metal. Its symbol is C.
• Carbon is a versatile element the percentage of carbon present in earth crust in form of mineral is 0.2% and in atmosphere as Co₂ is 0.03%.
• All the living things, plants and animals are made up of carbon based compounds.

Carbon always form covalent bonds :

The atomic number of carbon is 6.
Electronic configuration :

          K      L
  C(6) 2      4

How carbon attain noble gas configuration :

(i) Carbon is tetravalent, it does not form ionic bond by either losing four electronic (C⁴⁺) or by gaining four electronic (C^4-). It is difficult to hold four extra electron and would require large amount of energy to remove four electrons. So, carbon can form bond by sharing of its electrons with the electrons of other carbon atom or with other element and attain noble gas configuration.
(ii) The atoms of other elements like hydrogen, oxygen and nitorgen, chlorine also form bonds by sharing of electrons.
(iii) The bond formed by sharing of electrons between same or different atoms is covalent bond.

H - H single bond between hydrogen atoms

O = O double bond between oxygen atoms

N ≡ N triple bond between nitorgen atoms

Molecules of water has single covalent bond between one oxygen and two hydrogen atoms.

Physical Properties of Covalent Compounds :

(a) Covalent compounds have low melting and boiling points as they have weak intermolecular force.
(b) They are generally poor conductor of electricity as electrons are shared between atoms and no charged particles are fomed.

Versatile Nautre of Carbon :

The two characteristics properites of carbon element which lead to to the formation of large number of compounds :
(i) Catenation : Carbon can link with carbon atoms by means of covalent bonds to form long chains, branched chains and closed ring compounds. Carbon atoms may be linked by single, double or triple bonds.
(ii) Tetravalency : Carbon has 4 valence electorns. Carbon can bond wiht four carbon atoms, monovalent atoms, oxygen, nitorgen and sulphur.

Statured and Unsaturated Carbon Compounds :

Compounds made up of hydrangen and carbon are called hydrocarbon.

Hydrocarbon

Saturated	Unsaturated
• Single bond between carbon atoms.	• Double or triple bond between carbon atoms.
• - C - C -	• - C = C -        - C ≡ C-
• Alkanes   General formulae   Cn H2n + 2	• Alkenes          Alkynes   CnH2n             CnH2n-2

Electronic Dot Structure of Saturated Hydrocarbons :

The names, molecular formulae and sauturated formulae of saturated hydrocarbons (alkanes) are given below :

Name of Hydrocarbon	Moleculas Formula	Structural Formula
1. Methane	CH4	H | H - C - H | H
2. Elhane	C2H6	H H | | H - C - C - H | | H H
3. Propane	C3H8	H H H | | | H - C - C - C - H | | | H H H
4. Butane	C4H10	H H H H | | | | H - C - C - C - C - H | | | | H H H H
5. Pentane	C5H12	H H H H H | | | | | H - C - C - C - C - C - H | | | | | H H H H H

Electron Dot Structure of Unsaturated Hydrocarbons :

Name of Hydrocarbon	Moleculas Formula	Structural Formula
Alkenes :
1. Ethene	C2H4	H H | | H - C = C - H | | H H
2. Propane	C3H6	H H | | H - C = C - C - H | | H H
3. Butene	C4 H8	H H | | H - C = C - C - C - H | | | | H H H H
Alkynes :
1. Ethyne	C2H2	H - C ≡ C - H
2. Propyne	C3H4	H | H - C ≡ C - C - H | H
3. Butyne	C4H6	H H | | H - C = C - C - C - H | | H H

Carbon Compounds on the Basis of Structure :

(i) Straight (unbranched) chain

(ii) Branched

These three above compounds has same molecular formula but different structures are called structural isomers and phenomenon is structural isomerism.

(iii) Cyclic

Functional Groups

• In hydrocarbon chain, one or more hydrogen atom is replaced by other atoms in accordance with their valancies. These are heteroatom.
• These heteroatom or group of atoms which make carbon compound decides its properties are called functional groups.

Homologous Series :

It is series of compounds in which the some functional group substitutes for the hydrogen in a carbon chain.

E.g., Alcohols → CH₃OH,C₂H₅OH, C₃H₇OH, C₄H9OH
• Have same general formula.
• Any two homologous differ by - CH₂ group and difference in molecular mass is 14u.
• Have same chemical properites but show gradual change in physical properites.

Nomencalture of Carbon Compounds :

(i) Identify the number of carbon atoms in compounds.
(ii) Functional group is indicated by suffix or prefix.

Functional Group	Prefix/Suffix	Example
1. Halogen	Prefix - Chloro, Bromo, Iodo etc.	H H H | | | H - C - C - C - cl | | | H H H Chloro Propane
2. Alcohol	Suffix - ol	H H H | | | H - C - C - C - OH | | | H H H Propanaol
3. Aldehyde	Suffix - al	H H | | H - C - C - C = O | | | H H H Propanal
4. Ketone	Suffix - one	H H | | H - C - C - C - H | || | H O H Propanone
5. Carboxlic acid	Suffix - oic acid	H H O | | || H - C - C - C - OH | | H H Propanoic acid
6. Alkene (-C = C -)	Suffix - ene	H H | | H - C - C - C - H | | H H Propene
7. Alkyne(- C = C-)	Suffix-yne	H | H - C - C ≡ C - H | H Propyne

Chemical Properties of Carbon Compounds :

(a) Combustion

CH₄ + 2O₄ --Combustion→ CO₂ + 2H₂O + Heat + Light
• Carbon and its compounds are used as fuels becuase they burn in air releasing lot of heat energy.
• Saturated hydrocarbon generally burn in air with blue and non-sooty flame.
• Unsaturated hydrocarbon burns in air wiht yellow sooty flame because percentage of carbon is higher than saturated hydrocarbon which does not get completely oxidized in air.

(b) Oxidation

Alcohols can be converted to carboxylic acid in presence of oxidizing agent alkaline KMnO₄ (potassium permangnate) or acid potassium dichromate.

(c) Additon Reaction :

Unsaturated hydrocarbon add hydrogen in the presence of catalyst palladium or nickel. Vegetable oils are converted into vegetable ghee using this process. It is also called hydrogenation of vegetable oils.

(d) Susbtituton Reaction :

CH₄ + Cl₂ --Sunlight→ CH₃Cl + HCl

Important Carbon Compounds : Ethanol and Ethanoic acid

Physical Properties of Ethanol
• Colourless, pleasant smell and burning tast.
• Soluble in water.
• Volatile liquid with low boiling point of 351 K.
• Neutral compound.

Chemical Properties

(i) Reaction with Sodium :
     2Na + CH³CH₂OH → 2CH₃CH₂ONa + H₂
                                         (Sodium ethoxide)
This reaction is used as a test for ethanol by evolution of H₂ gas (Burn with pop sound).

(ii) Dehydration :
      CH₃ CH₂OH --Hot conc.H₂SO₄→ CH₂ = H₂O

Physical Properties of Ethanoic acid

• Colourless liquid having sour taste and have smell of vinegar.
• Boiling point is 391 K.
• When pure CH₃COOH is freezed, it forms colouless ice like solid. So it is called glacial acetic acid.

Chemical Properties

(i) Esterification :
     CH₃COOH + CH₃CH₂OH --Acid→ CH₃   CO   CH₂   CH₃ + H₂O
     (Ethanoic acid) (Ethanol)                              ||
                                                                           O
                                                                          Ester

     Sweet smelling ester is formed.
     CH₃  CO  CH₂ CH₃ + NaOH → CH₃COONa + CH₃CH₂OH
              ||
             O
     This is saponification as soap is prepared by this.

(ii) Reaction with base :
      NaOH + CH₃COOH → CH₃COONa + H₂O

(iii) Reaction with carbonates and hydrogen carbonates :
      2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
      CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂
                                                  (Sodium acetate)

Soaps and Detergents

• Soap is sodium or potassium salt of long chain carboxylic acid. E.g, C₁₇H ₃₅COONa⁺
• Soaps are effective only in soft water.
• Detergents are ammonium or sulphonate salt of long chain fo carboxylic acid.
• Detergents are effective in both hard and soft water.

Soap molecule has :
(i) Ionic (hydrophilic) part
(ii) Long hydrocarbon chain (hydrophilic) part.

Cleaning Action of Soap :

• Most dirt is oily in nautre and hydrophobic end attaches itself with dirt and he ionic end is surrounded with molecule of water. This results in formation of a radial structure called micelles.
• Soap micells helps to dissolve dirt and grease in water and cloth gets cleaned.

• The magnesium and calcium salt present in hard water react with soap molecule to form insoluble product called scum. This sum create difficultly in cleansing action.
• By use of detergent, insoluble scum is not formed with hard water and cloths get cleaned effectively.