Carbon And Its Compounds | CBSE Class 10th Chemistry Notes

Carbon and its Compounds

  • Carbon dioxide is present in the atmosphere(0.03%) and in the form of minerals(0.02%).
  • Almost all organisms are carbon-based.

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Acids Bases And Salts 

Chemical Reactions and Equations

Covalent bonding in Carbon Compounds.

Electronic configuration of carbon (atomic no. 6) is  K  L

                                                                                             2  4

It can complete its octet in two ways:-

  • It could lose 4 electrons, which is not possible as a large amount of energy is required to remove 4 electrons and form a positive ion.
  • It could gain 4 electrons but it’s difficult for 6 protons to hold 10 electrons, it’s not possible.
  • So carbon shares its electron with others atoms, and the type of bond formed is called a covalent bond.
Covalent Bond
Covalent Bond

Covalent bonds are 3 types depending on no. of electrons shared:

Single covalent bond:

The bond is formed when 1 pair of electrons are shared between the atoms.

Example: hydrogen, chlorine, etc.

Double covalent bond:

The bond is formed when 2 pairs of electrons are shared between the atoms.

Example: oxygen

Triple covalent bond:

The bond is formed when 3 pairs of electrons are shared between the atoms.

Example: nitrogen etc.

Covalent Bonds
Covalent Bonds

Properties of Covalent Bonds

  • Covalent bonds have a low melting and boiling point because of weak forces of attraction between the atoms.
  • They are insoluble in water but soluble in organic solvents.
  • They are poor conductors of electricity because of a lack of free ions.
  • They are liquids and gases except for graphite and diamond.

Carbon is able to make a large number of compounds as compared to other elements. This is possible as Carbon has 2 important property i.e catenation and tetravalency.

Catenation

The property by which elements make bonds with other atoms of the same elements. Carbon is having this property and makes bonds with C-atoms.

Carbon forms long, straight, or branched chains and rings. As compared to other elements only Carbon has maximum catenation property.

Tetravalency

The electronic configuration of Carbon is 2,4, so its valency is 4. Due to this, it is able to make bonds with 4 other carbon atoms. Not only with carbon it can form bonds with other elements like hydrogen, chlorine, etc.

Carbon due to its small size it can form multiple bonds ( double and triple).

Hydrocarbons

The compounds which contain only carbon and hydrogen are called hydrocarbons. Ex: CH4 , C2H6 etc.

Hydrocarbons can be classified in the following ways:

  • Saturated hydrocarbons: These are the hydrocarbons in which carbon and hydrogen atoms are bonded by a single bond. These are known as Alkane with the general formula CnH2n+2
  • Saturated hydrocarbons: These are the hydrocarbons in which carbon and hydrogen atoms are bonded by a single bond. These are known as Alkane with the general formula CnH2n+2

Alkene doesn’t exist with one carbon atom and Alkyne has a minimum of 2 no. of carbon atoms.

Steps to draw the structure of carbon compounds:

  • First connect all the carbon atoms with a single bond.
  • Then use hydrogen atoms to satisfy the valencies of all the C-atoms.
  • If hydrogen atoms are less than the required atoms, then satisfy the valencies with double and triple bond.
  • Similar method can be used to form carbon compounds in ring or cyclic structure.

Electron Dot structure

  • Write the valence electrons of the element , represent it in the form of dots
  • Place the least electronegative element in the centre and draw the bonds from the centre to other atoms.
  • Satisfy the electron requirement of the elements.

If not satisfied add double or triple bonds.   

Electron Dot Structure | Lewis Structure
Electron Dot Structure

Saturated compounds formulae and structures:

Saturated Compounds
Saturated Compounds
Hydrocarbons
Structure of Repr. Hydrocarbons

Structural Isomerism

The compounds have the same molecular formula but different structures.

Example: There are 2 isomers of butane

Isomers of Butane
Isomers of Butane

Functional groups

Carbon can also make bonds with other elements like halogens, oxygen, nitrogen, etc. These elements are called heteroatoms. Functional groups are the group of atoms that decide the properties and reactivity.

Some important functional groups are given below:

Functional Group
Functional Group

Homologous Series

A series in which the members involved have the same chemical properties and same functional group and the difference between two successive members is CH2 unit.

Example: CH4, C2H6, CEH8 etc, are the members of alkane family.

  • All the members in the homologous series have the same chemical properties but different physical properties like melting and boiling point.
  • They can be represented by the same general formula.
  • Two successive members differ by 14 u.

Writing name for the compound

Count the no. of carbon atoms and write it in root word given as follows:

Root Word
Root Word
  • If the compound has a single bond add suffix “ane”, but if the compound has a double or triple bond add suffix “ene” or “yne”
  • If the compound contains a functional group then follow the table to write the name:
Prefix and Suffix
Prefix and Suffix

Chemical properties of carbon compounds

Almost all the carbon compounds burn in presence of oxygen to form CO2 and H2O. Also in the process lot of heat and light are generated. This process is known as combustion.

Example: CH4 + 2O2 = CO2 + H20 + Heat + Light

Carbon compounds are used as fuel. Saturated compounds burn completely and give a clean blue flame.

On the other hand, unsaturated compounds don’t burn completely and give black smoke and yellow flame. Also, saturated compounds when supplied with less oxygen burns with a sooty flame.

Oxidation

The process of the addition of oxygen or removal of hydrogen is called oxidation. Alcohols when heated in I presence of alkaline KMnO4 or acidified K2Cr2O7 get oxidized to carboxylic acid.

Ethanoic Acid

Addition reactions

A reaction in which reagents completely add to a reactant without any removal of molecules.

Example: The addition of hydrogen in the presence of catalysts like nickel or pallidum to an unsaturated hydrocarbon will yield saturated hydrocarbon.

Addition Reaction
Addition Reaction

Substitution Reactions

The reaction in which an atom replaces another atom from reactant is called substitution reaction. The reaction mostly takes place in presence of sunlight also chlorine is added to the reaction.

Example: CH4 + Cl2 + Sunlight = CH3Cl + HCl

Ethanol

The common name of Ethanol is Ethyl alcohol. Its formula is C2H5OH or CH3CH2OH. It is prepared by the process of fermentation of molasses.

  • It is liquid at room temperature.
  • It is soluble in water.
  • Its melting point is 156 K and boiling point is 351 K.

Chemical Properties

  • Ethyl alcohol reacts with sodium to form sodium ethoxide and H2 gas. 2Na + 2CH3CH2OH = 2CH3CH2ONa + H2
  • Dehydration: The removal of hydrogen from a compound is called dehydration. When ethanol is heated with concentrated H2SO4 at 443 K then water is removed and ethene is obtained.
Dehydration
Dehydration

Uses

  • It is used in making alcohol.
  • It is used in making medicine like tincture of iodine , syrup etc.
  • It is used in radiators of vehicles.

Ethanoic acid

It is also known as acetic acid and its formula is CH3COOH.

Physical properties

  • It is stronger than alcohol but weaker than HCl.
  • It melting point is 290 K
  • In winter it freezes to form glacial acetic acid also known as anhydrous acetic acid.

Chemical Properties

  • Acidity: It is more acidic than alcohol because of the stability of the ion whereas it is less acidic than HCl because of low ionization. When sodium metal reacts with it and hydrogen gas is released. 2CH3COOH + 2Na = 2CH3COONa + H2
  • Reaction with a base: It reacts with a base to give salt and hydrogen gas. CH3COOH + NaOH = CH3COOHNa + H20
  • Esterification: When acetic acid reacts with ethanol in presence of catalyst-like acid then a smelling liquid is obtained called an ester. This reaction is called esterification
Esterification
Esterification

The ester obtained is treated with sodium hydroxide and gets converted into alcohol and sodium salt of the acid. This reaction is called is Saponification which is used in making soap.

Making Soap
  • Reaction with carbonates and hydrogen carbonates: Acetic acid reacts with carbonates and hydrogen carbonates to release CO2. Example:

       CH3COOH + NaHCO3 = CH3COOHNa + H2O + CO2

        2CH3COOH + Na2CO3 = 2CH3COOHNa + H20 + CO2

Uses

  • It is used to preserve pickels
  • It is used in making vinegar
  • It is used in making other compounds like esters.

Soaps and Detergents

  • Soaps are the long chain carboxylic acids of sodium and potassium and their general formula is RCOONa, where R=C15H31 , C17H35 etc.
  • Detergents are the long chain of carboxylic acids of sulphonate or ammonium salts.  They are also known as soapless soap.
  • Soaps are usually made of animals fats and or vegetable oils by heating them with NaOH. This process is called saponification.

     Fat or Oil + Alkali + Heat = Soap + Glycerol

      (easter)       (NaOH )                 (An alcohol)

     Structure of soap molecule

  • A soap molecule has 2 major part- a hydrocarbon part and a short ionic part containing COONa group
  • The hydrocarbon part is called hydrophobic and the ionic part is called hydrophilic.
hydrocarbon part

Soaps: Cleaning action

  • The soaps have 2 ends hydrophilic and hydrophobic. The hydrophobic end will be insoluble in water and they align themselves along the surface of the water with the ionic end in the water and tail protruding out of water.
  • Clusters are formed in which the hydrophobic end is inside the cluster whereas ionic ends are on the surface of the cluster. This cluster is called a micelle.
  • To clean the dirty clothes, micelles are either scrubbed mechanically or agitated in washing machines. Due to micelles, soaps clean the clothes as the dirt is collected in the middle of the micelle.
Micelle
Micelle
  • The calcium and magnesium salts react with water to form an insoluble substance known as scum. The formation of scum affects the cleansing action of soap.
  • In such a situation, detergents are used which are the sodium salts of sulphonic acids or ammonium salts with chlorides, etc. These detergents are very effective in hard water as compare to soaps.

Credit: Notes Prepared by – Abhay Tiwari

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