NCERT Solutions Class 10th Science Chapter – 4 Carbon and its Compounds Notes

NCERT Solutions Class 10th Science Chapter – 4 Carbon and its Compounds

NCERT Solutions Class 10th Science Chapter – 4 Carbon and its Compounds

Chapter – 4

Carbon and its Compounds

Notes

COVALENT BOND IN CARBON • The atomic number of carbon is 6 and its electronic configuration is 2,4. To attain a noble gas configuration it can 1. Gain 4 electrons – But it would be difficult for nucleus to hold 4 extra electrons, and is highly energy requiring process. 2. Lose 4 electrons – But it would require a large amount of energy to remove 4 electrons. • It is difficult thus for an atom of carbon to either gain or lose electrons. • Carbon attains the noble gas configuration by sharing its valence electrons, with other atoms. Atoms of other elements like hydrogen, oxygen, nitrogen, chlorine also show sharing of valence electrons. • Shared electrons belong to the outer shells of both atoms, which there by achieve noble gas configuration. Formation of H2, O2, and N2 is shown as below: (i) H2 Molecule (ii) O2 Molecule (iii) N2 Molecule • It is evident that the number of shared pair of electrons can be one, two or three. • Bond formed by the sharing of an electron pair between two atoms is called covalent bond. • Covalently bonded molecules have low melting and boiling points because of comparatively weaker intermolecular forces, unlike ionic compounds. • These molecules are generally poor conductor of electricity since no charged particles are formed.

VERSATILE NATURE OF CARBON ATOMS Three important properties of carbon atom enable carbon to form enormously large number of compounds.   CATENATION – property of carbon atom to form bond with other atoms of carbon is called catenation. Like. carbon, silicon forms compounds with hydrogen upto seven or eight atoms of silicon. TETRAVALENCY – Having a valency of 4, carbon atom is capable of bonding with atoms of oxygen, hydrogen, nitrogen, Sulphur, chlorine and other elements. The smaller size of carbon atom enables nucleus to hold the shared pair of electrons strongly, thus carbon compounds are stable in general.

Saturated and Unsaturated Carbon Compounds • To have a double/triple bond in chain, at least two carbon atoms are required. So, first member of alkene and alkyne have two-carbon atoms. • Electron dot structure of a saturated carbon compound, ethane (C2H6) • Electron dot structure of an unsaturated carbon compound, ethene (C2H4) and ethyne (C2H2) • Formulae and structure of saturated compounds of carbon and hydrogen.

On the basis of structures the hydrogcarbons can be

S.no.	Name	Formula	Structure
1.	Methane	CH4
2.	Ethane	C2H6
3.	Propane	C3H8
4.	Butane	C4H10
5.	Pentane	C5H12

S.no.	No. of hydrocarbon (Alkene)	Formula	Structure
1.	Methane	C2H4
2.	Propene	C3H6
3.	Butene	C4H8

S.no.	No. of hydrocarbon (Alkene)	Formula	Structure
1.	Ethyne	C2H2
2.	Propyne	C3H4
3.	Butyne	C4H6

Cyclic Structure Structural isomers – these are the compounds having Identical molecular formula but different structures.

Heteroatom	Function Group	Formula
Cl/Br	Halo (Chloro/Bromo)	-Cl, -Br (Substitutes For hydrogen atom)
Oxygen	1. Alcohol	-OH
	2. Aldehyde
	3. Ketone
	4. Carboxylic acid

2. Oxidation Alcohols can be converted to carboxylic acid by oxidizing them using alkaline potassium permanganate or acidified Potassium dichromate (they add oxygen to the reactant, thus are called oxidizing agents)

3. Addition Reaction: Hydrogen is added to unsaturated hydrocarbon which are more reactive due to double/triple bond, in presence of nickel platinum or palladium as catalyst. This process is called hydrogenation. Vegetable oils are converted into vegetable ghee using this process. Hydrogenation slows the rancidity of vegetable oils. Saturated fatty acids are harmful for health and oils with unsaturated fatty acids should be used for cooking.

4. Substitution Reaction In saturated hydrocarbons, the hydrogen attached to carbon can be replaced by another atom or group if atoms in presence of light or heat.

SOAPS AND DETERGENTS • Soap is sodium and potassium salt of carboxylic acids with long chain. (C15H31 COOH), (C17H35COOH) (Palmitic acid, stearic acid). • Soaps are effective with soft water only and ineffective with hard water. • Detergents are ammonium or sulphonate salts of hydrocarbons with long chain, they are effective with both soft as well as hard water. • An ionic part (hydrophillic) and a long hydrocarbon chain (hydrophobic) part constitutes the soap molecule.

STUCTURE OF A SOAP MOLECULE Cleansing action of Soaps – • Most dirt is oily in nature and the hydrophobic end attaches itself with dirt, while the ionic end is surrounded with molecules of water. This result in formation of a radial structure called micelles. • An emulsion is thus formed by soap molecule. The cloth needs to be mechanically agitated to remove the dirt particles from the cloth. • Scum – The magnesium and calcium salts present in hard water reacts with soap molecule to form insoluble products called scum, thus obstructing the cleansing action. Use of detergents overcome this problem as the detergent molecule prevents the formation of insoluble product and thus clothes get cleaned. • Soaps are completely biodegradable, while detergents are not. Soaps are environmental friendly but detergents are not.

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