4. Carbon and its Compounds Science class 10 exercise Soap And Detergents
4. Carbon and its Compounds Science class 10 exercise Soap And Detergents ncert book solution in english-medium
NCERT Books Subjects for class 10th Hindi Medium
Presence of carbon | bonds in carbon | Catenation
Chapter 4. Carbon And its Nature
Introduction of Carbon:
Carbon is a non-metal element. its chemical symbol is C and atomic number is 6. There are three naturally presence of its isotopes, which are 12C, 13C and 14C. Its electronic configuration is 2, 4 and valency is 4. Hence it is tetravalent.
Food, clothes, medicines, books, or many of the things that you listed are all based on this versatile element carbon. In other hand, all living structures are carbon based.
Presence:
Carbon forms very large numbers of compound in nature. The earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, hydrogencarbonates, coal and petroleum) and the atmosphere has 0.03% of carbon dioxide. Carbon is common element which is found in universe and forms many different compounds. The many non-living and living things surrounding us made up of carbon and its compound like plants animals, sugar, fuels, papers, foods, textiles, fabrics, medicines, cosmetics etc. These all are organic compounds which either derived from plants or animals origin. The chemistry of organic compounds is known as Organic Chemistry.
Allotropes of carbon:
Allotrope: An element, in different forms, having different physical properties but similar chemical properties is known as allotropes of that element.
Carbon has three well known allotropes which are graphite, daimond and buck minster fullerene. These are formed by carbon atoms.
In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array. One of these bonds is a double-bond, and thus the valency of carbon is satisfied. Graphite structure is formed by the hexagonal arrays being placed in layers one above the other. Graphite is also a very good conductor of electricity unlike other non-metals
In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure. Diamond is the hardest substance known while graphite is smooth and slippery. Diamonds can be synthesised by subjecting pure carbon to very high pressure and temperature. These synthetic diamonds are small but are otherwise indistinguishable from natural diamonds.
Fullerenes form another class of carbon allotropes. The first one to be identified was C-60 which has carbon atoms arranged in the shape of a football. Since this looked like the geodesic dome designed by the US architect Buckminster Fuller, the molecule was named fullerene.
BONDING IN CARBON:
Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration. If it were to gain or lose
electrons –
(i) It could gain four electrons forming C4– anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons, that is, four extra electrons.
(ii) It could lose four electrons forming C4+ cation. But it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons.
Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements. Not just carbon, but many other elements form molecules by sharing electrons in this manner.
Chemical Bond: The force exerts between two atoms of elements is called chemical bond.
(i) Ionic Bond: The bond formed by transfering electrons completly is called ionic bond.
Na+ + Cl- -------> NaCl
(ii) Covalent Bond: Bonds which are formed by the sharing of an electron pair between two atoms are known as covalent bonds.
Types of Covalent Bond:
There are three types of covalent bond.
(A) Single Covalent Bond: A covalent bond formed by sharing of one electron pair between two atoms is called a single covalent bond. A single bond is also represented by a line between the two atoms ( - ).
Example: H - H, Cl - Cl, Br - Br
(B) Double Covalent Bond: A covalent bond formed between two atoms by sharing of two electron pairs ia called dauble covalend bond. It is denoted by dauble short lines (=).
O=O [oxygen to oxygen]
(C) Triple Covalent Bond: A covalent bond formed by sharing of three electrons between two atoms is called triple covalent bond. It is denoted by triple short lines (≡).
N ≡ N [Nitrogen to nitrogen]
Properties of Compound formed by Covalent Bond:
(i) Covalently bonded molecules are seen to have strong bonds within the molecule.
(ii) intermolecular forces are small.
(iii) These have low melting and boiling points of these compounds.
(iv) These compounds are generally poor conductors of electricity.
Some Other Properties of Carbon:
1. Catenation: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation.
The nature of the covalent bond enables carbon to form a large number of compounds.
2. Tetravalency: Carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element. This property of carbon is known as tetravalency of carbon.
Somes Features of Carbon Bond:
(i) Carbon forms with most other elements are very strong making these compounds exceptionally stable.
(ii) One reason for the formation of strong bonds by carbon is its small size.
(iii) This enables the nucleus to hold on to the shared pairs of electrons
strongly.
Differences between bonds formed by carbon and other larger atoms:
the formation of strong bonds by carbon is its small size. This enables the nucleus to hold on to the shared pairs of electrons strongly. The bonds formed by elements having larger atoms are much weaker.
A Large number of Organic Compounds are formed by carbon:
A Large number of Organic Compounds are formed by carbon in nature due to its following features:
(i) Forming covelent bond : Carbon makes a large number of compound in nature due to form covelent bond.
(ii) Catenation: The carbon-carbon bond is very strong and hence stable. This gives us the large number of compounds with many carbon atoms linked to each other.
(iii) Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element.
What happens Forming C4- and C4+ by carbon:
Normaly there are two condition with carbon to form ionic bond to gain 4 electrons or lose 4 electrons.
(i) It could gain four electrons forming C4– anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons, that is, four extra electrons.
(ii) It could lose four electrons forming C4+ cation. But it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons.
What to do carbon to overcome this problems:
Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements. Not just carbon, but many other elements form molecules by sharing electrons in this manner. The shared electrons ‘belong’ to the outer shells of both the atoms and lead to both atoms attaining the noble gas configuration.
Hydrocarbons | Alkane | Alkene | Alkyne
Hydrocarbons
Hydrocarbons: All carbon compounds which contain just carbon and hydrogen are called hydrocarbons.
Formulae of organic compounds:
(i) General formula: General formula represents a function for n numbers of each atom in a molecule.
Example: for alkane: CnH2n+2
(ii) Molecular formula: Molecular formula represents actual number of atoms of a molecule.
Example: For Ethane: C2H6
(iii) Condensed formula: Condensed formula represents group of atoms linked together to each carbon atom.
Example: For Ethane: CH3CH3
(iv) Structural formula: It represents exact arrangement of atom of a molecule.
Example: For Ethane:
(v) Electronic formula: Electronic formula represents the sharing of electrons amongs atoms of a molecules.
Example: For Ethane:
Saturated Carbon Compounds:
Compounds of carbon, which are linked by only single bonds between the carbon atoms are called saturated compounds.
Example: Alkanes like methane, Ethane, propane butane etc.
General formula for Alkanes: CnH2n+2
Using formula for Methane;
CnH2n+2
Putting n =1 we get
C1H2x1 + 2
CH4
Similarily;
For Ethane:
Putting n =2 we get
C2H2x2 + 2
C2H6
Similarily we can find molecular formula for propane, butane, pentane and so on .......
Alkanes: The saturated hydrocarbons in which carbon atom linked together with single bond are called alkenes.
Name of Alkanes | Molecular Formula | Condensed structural Formula |
Methane | CH4 | CH4 |
Ethane | C2H6 | CH3CH3 |
Propane | C3H8 | CH3CH2CH3 |
Butane | C4H10 | CH3CH2CH2CH3 |
Pentane | C5H12 | CH3CH2CH2CH2CH3 |
Hexane | C6H14 | CH3CH2CH2CH2CH2CH3 |
Heptane | C7H16 | CH3CH2CH2CH2CH2CH2CH3 |
Octane | C8H18 | CH3CH2CH2CH2CH2CH2CH2CH3 |
Nonane | C9H20 | CH3CH2CH2CH2CH2CH2CH2CH2CH3 |
Decane | C10H22 | CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 |
Structure of Methane (single bond);
Single carbon atom has four unsatisfied valency Linked with Hydrogen atom like figure.
Electrone Dot strucuture of Methane
Structure of Ethane (single bond);
C - C [ carbon atoms linked together witha single bond]
Next Linked with Hydrogen atom to carbon unsatisfied valency like given figure;
Electron Dot structure of Ethane
Structure of propane (single bond);
Structure of Butane (single bond);
Structure of pentane (single bond);
Structure of hexane (single bond);
Unsaturated Carbon Compounds:
Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated compounds.
Example: Alkenes like and Alkynes;
Structure of alkenes (Double bond);
General Formula for Alkenes: CnH2n
The simplest Alkenes is Ethene;
So Ethene has 2 carbon atoms;
Now putting n = 2 in general formula;
C2H2x2 = C2H4
Propene has 3 carbon atoms;
Now putting n = 3 in general formula;
C3H2x3 = C3H6
Similarily we can find the molecular formula for other Alkenes like butene, pentene and hexene etc.
Alkenes: The unsaturated hydrocarbons which contain one or
more double bonds are called alkenes.
Name of Alkenes | Molecular Formula | Condensed structural Formula |
Ethene | C2H4 | CH2=CH2 |
Propene | C3H6 | CH3CH=CH2 |
Butene | C4H8 | CH3CH2CH=CH2 |
Pentene | C5H10 | CH3CH2CH2CH=CH2 |
Hexene | C6H12 | CH3CH2CH2CH2CH=CH2 |
Heptene | C7H14 | CH3CH2CH2CH2CH2CH=CH2 |
Octene | C8H16 | CH3CH2CH2CH2CH2CH2CH=CH2 |
Nonene | C9H18 | CH3CH2CH2CH2CH2CH2CH2CH=CH2 |
Decene | C10H20 | CH3CH2CH2CH2CH2CH2CH2CH2CH=CH2 |
Structural Formula of Alkene:
Name of Alkenes | Molecular Formula | Structural Formula |
Ethene | C2H4 | |
Propene | C3H6 | |
Butene | C4H8 | |
Pentene | C5H10 | |
Hexene | C6H12 | |
Heptene | C7H14 | |
Octene | C8H16 | |
Nonene | C9H18 | |
Decene | C10H20 | |
Electron Dot Sructure of Ethene:
Ethene (C2H4)
Electron Dot Sructure of Propene:
Prooene (C2H4)
Similarily We can draw electron dot structure of other Akenes;
Structure of Alkynes (Triple Bond):
General formula of Alkynes: CnH2n-2
The simplest alkynes is Ethyne;
Ethyne has two carbon atoms. Hence, Using the formula;
Putting n = 2 for Ethyne,
C2H2x2-2 = C2H2
∴ Ethyne = C2H2
Similarily we can find Propyne;
Putting n=3 for Propyne;
C3H2x3-2 = C3H4
∴ Propyne = C3H4
Alkynes:
Name of Alkenes | Molecular Formula | Condensed structural Formula |
Ethyne | C2H2 | CH≡CH |
Propyne | C3H4 | CH≡CCH3 |
1-Butyne | C4H6 | CH≡CCH2CH3 |
1-Pentyne | C5H8 | CH≡CCH2CH2CH3 |
1-Hexyne | C6H10 | CH≡CCH2CH2CH2CH3 |
1-Heptyne | C7H12 | CH≡CCH2CH2CH2CH2CH3 |
1-Octyne | C8H14 | CH≡CCH2CH2CH2CH2CH2CH3 |
1-Nonyne | C9H16 | CH≡CCH2CH2CH2CH2CH2CH2CH3 |
1-Decyne | C10H18 | CH≡CCH2CH2CH2CH2CH2CH2CH2CH3 |
Long chain formula is abbreviated as bellow;
[Nonyne] CH≡CCH2CH2CH2CH2CH2CH2CH3 can be written as
CH≡C (CH2)6CH3
similarily;
[Decyne] CH≡CCH2CH2CH2CH2CH2CH2CH2CH3 can be written as
CH≡C (CH2)7CH3
Defferences between saturated and unsaturated carbon compound:
Saturated Compound | Unsaturated Compound |
1. It has single bond between carbon atoms. 2. There occurs substitution reaction in it. 3. Example: Alkanes. 4. They are less reactive than the unsaturated carbon compound. |
1. It has double and triple bond between carbon atoms. 2. There occurs addition reaction in it. 3. Example: Alkenes, Alkynes. 4. They are more reactive than the saturated carbon compounds. |
Making Carbon Skeletons:
Making Carbon Skeletons:
Skeletons of Carbon Atoms:
(i) Straight Carbon chain: When carbon atoms are linked together in staight chain.
E.g:
C-C-C-C
(ii) Branches Carbon chain: When carbon atoms are linked together in staight chain.
E.g:
(iii) Ring Carbon chain: When carbon atoms are linked together in ringh shape.
E.g:
Structural Isomers:
Compounds with identical molecular formula but different structures are called structural isomers.
Example 1: Structural Isomers of Butane; Whoose molecular formula is C4H10.
Structure Isomer (I) of Butane Structure Isomer (II) of Butane
Example 2: Structural Isomers of Butene (double bond); Whoose molecular formula is C4H8.
Structure Isomer (I) of Butene Structure Isomer (II) of Butene
Ring Skeletons in Hydrocarbons:
Structure of cyclohexane molecule (C6H12)
Structure of Benzene Molecules (C6H6)
Functional Group and Nomenclature of Hydrocarbons
Chapter 4. Carbon And Its Compounds
Functional Group:
Functional group is a group of an atom or atoms in any carbonic compound which are bonded each other in special manner. That is generally region of chemical reactivity in carbonic atoms.
Oxygen, chlorine, sulpher, nitrogen and other elements can be presence as a part of a functional group in carbonic compounds.
Hetroatoms: The element which replaces hydrogen in a compound is called hetroatom.
Example: Oxygen, chlorine, sulpher, nitrogen and other elements can be presence as a part of a functional group in carbonic compounds, such elements are called hetroatoms.
Some List of Functional Groups:
(i) Halogen: Halogens are non-metal elements like fluorine, chlorine, bromine and Iodine etc situated in modern periodic table in group 17.
Functional Group | formula of functional group | Hetroatom |
Halogen |
-Cl (Sufix is used Chloro) -Br (Sufix is used Bromo) -I (Sufix is used Iodo) |
Cl (Chlorine) Br (Bromine) I (Iodine) |
(ii) Alcohol: Alcohol is another function group which joining to a series of hydrocarbon forms the group of atoms
Example: - OH
(-OH) joins to hydrocarbon like alkane form various type of alcohols, such methanol, ethanol and propanol etc.
(iii) Aldehyde: It is a functional group in which carbon atom linked with a single oxygen atom in double bond along with one hydrogen atom.
(iv) Ketone: Ketone is also a functional group which joins to hydrocarbons form a series of molecules. In ketone carbon atom linked with a single oxygen atom in double bond.
(v) Carboxylic acid: It is also a functional group, in which a carbon atom is linked with oxygen atom in double bond and also linked with hydroxide.
Homologous Series:
A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.
Examples:
Carbon chain with alkane | Homologous Series with halogen (-Cl) | Homologous Series with halogen (-Br) | Homologous Series with halogen (-I) | Homologous Series with Alcohol (-OH) | Homologous Series with Aldehyde (-CHO) | ||
CH4 | CH3-Cl | CH3-Br | CH3-I | CH3-OH | H-CHO | ||
C2H6 | C2H5-Cl | C2H5-Br | C2H5-I | C2H5-OH | CH3-CHO | ||
C3H8 | C3H7-Cl | C3H7-Br | C3H7-I | C3H7-OH | C2H5-CHO | ||
C4H10 | C4H9-Cl | C4H9-Br | C4H9-I | C4H9-OH | C3H7-CHO | ||
C5H12 | C5H11-Cl | C5H11-Br | C5H11-I | C5H11-OH | C4H9-CHO | ||
C6H14 | C6H13-Cl | C6H13-Br | C6H13-I | C6H13-OH | C5H11-CHO |
Increasing in molecular Mass in Homologous series:
As the molecular mass increases in any homologous series, a gradation in physical properties is seen. This is because the melting points and boiling points increase with increasing molecular mass. Other physical properties such as solubility in a particular solvent also show a similar gradation. But the chemical properties, which are determined solely by the functional group, remain similar in a homologous series.
Nomenclature of carbon Compounds:
Naming of organic compound systematically called as nomenclature.
IUPAC Name:
Name formed by this nomenclature is called IUPAC name of molecules.
Nomenclature of Hydrocarbons:
According to presence of carbon atoms in hydrocarbon molecules naming of molecules are as follows:
No. of carbon atoms | Name | Example With Alkane (H.C) |
1 carbon atom | Meth- | Methane |
2 carbon atoms | Eth- | Ethane |
3 carbon atoms | Prop- | Propane |
4 carbon atoms | But- | Butane |
5 carbon atoms | Pent- | Pentane |
6carbon atoms | Hex- | Hexane |
7 carbon atoms | Hept- | Heptane |
8 carbon atoms | Oct- | Octane |
9 carbon atoms | Non- | Nonane |
10 carbon atoms | Dec- | Decane |
We have already known that Hydrocarbons are three types and their nomenclature are as follows:
(i) Alkane (Single bond):
Functional Group Halogen and its nomenclature:
For -(Cl) "chloro" is used, (-Br) "Bromo" is used and (-I) "Iodo" is used.
(A) Alkane with Chlorine
Molecular formula of F.G halogen (chlorine) | IUPAC Name | |
CH3-Cl | Chloro-methane | |
C2H5-Cl | Chloro-ethane | |
C3H7-Cl | Chloro-propane | |
C4H9-Cl | Chloro-butane | |
C5H11-Cl | Chloro-pentane | |
C6H13-Cl | Chloro-hexane |
(B) Alkane with Bromine
Molecular formula of F.G halogen (Bromine) | IUPAC Name | |
CH3-Br | Bromo-methane | |
C2H5-Br | Bromo-ethane | |
C3H7-Br | Bromo-propane | |
C4H9-Br | Bromo-butane | |
C5H11-Br | Bromo-pentane | |
C6H13-Br | Bromo-hexane |
(C) Alkane with Iodine
Molecular formula of F.G halogen (Bromine) | IUPAC Name | |
CH3-I | Iodo-methane | |
C2H5-I | Iodo-ethane | |
C3H7-I | Iodo-propane | |
C4H9-I | Iodo-butane | |
C5H11-I | Iodo-pentane | |
C6H13-I | Iodo-hexane |
Functional Group Alcohol and its nomenclature:
To give the name to Alcohol group we use a "suffix" -"ol" With the name of simple Alkane
(D)Alcohol
Molecular formula of F.G Alcohol (-OH) | IUPAC Name | |
CH3-OH | Methanol | |
C2H5-OH | Ethanol | |
C3H7-OH | Propanol | |
C4H9-OH | Butanol | |
C5H11-OH | Pentanol | |
C6H13-OH | Hexanol |
Note: Above Examples (A), (B), (C) and (D) are also Homologous series:
(ii) Alkene (Double bond)
(iii) Alkyne (Triple bond)
Chemical Properties of Carbon Compounds
Chapter 4. Carbon and its Compounds
Combustion: Combustion is the burning of compounds in air to give CO2 and water.
(i) Combustion of Methane (CH4) in air the reaction is as follows:
CH4 + 2O2 → CO2 + 2H2O + heat and light
(ii) Combustion of Ethanol (CH3CH2OH) in air gives CO2 water, heat and light.
CH3CH2OH + 3O2 → 2CO2 + 3H2O + heat and light.
Above example you have seen that how carbon compounds release heat and light on burning.
Carbon Compound As Fuels:
The most carbon compounds release a large amount of heat and light on burning.
Oxidation: Oxidation is a reaction in which carbon compounds take up oxygen in the presence of oxidising agents to form another carbon compound.
Oxidising Agent: some substances are capable of adding oxygen to others.
These substances are known as oxidising agents. Example: Alkaline potassium permanganate and acidified potassium dichromate are oxidising agent.
Oxidation of ethyle Alcohol by Alkaline potassium permanganate or acidified potassium dichromate:
When some drops of alkaline potassium permanganate o acidified potassium dichromate is added with heated ethyle alcohol it get oxidised and a complete oxidation takes place and it forms acetic acid.
The equation of this reaction is as follows:
Addition Reaction: An atom or group of atoms are added to an unsaturated compound.
"The reaction in which adds the substances is known as Addition reaction."
This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst.
Catalysts: Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction itself being affected.
Unsaturated hydrocarbons add hydrogen in the presence of catalysts
such as palladium or nickel to give saturated hydrocarbons.
For Example:
Hydrogenation Reaction:
Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons is called hydrogenation. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst in industry.
Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains.
Which is better, and Why?
Unsatuared fatty acids (vegetable oils) are ‘healthy’. Animal fats generally contain saturated fatty acids which are said to be harmful for health. Oils containing unsaturated fatty acids should be chosen for cooking.
Substitution Reaction: An atom or group of atom or a group present in a saturated compound is replaced by another atom or group.
Chlorine is a hetroatom which removes hydrogen from carbon compound.
Example of substitution reaction:
When chlorine is added to hydrocarbons in the presence of sunlight It replaces hydrogen atoms one by one. This is very fast reaction. Chlorine forms functional group of halogen.
Example: When chlorine (Cl2) is added to Methane (CH4), this reaction gives chloro-methane and hydrochloric acid. [Here substitution of hydrogen is taken place by chlorine]
CH4 + Cl2 → CH3Cl + HCl (in the presence of sunlight)
Chemical properties of carbon compounds:
Chemical properties of carbon compounds are followings;
(i) Carbon, in all its allotropic forms, burns in oxygen to give carbon dioxide along with the release of heat and light.
(ii) Most carbon compounds also release a large amount of heat and light on burning.
(iii) Carbon compounds can be easily oxidised on combustion.
(iv) Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons.
(v) Saturated hydrocarbons are fairly unreactive and are inert in the presence
of most reagents.
Features of saturated and unsaturated hydrocarbons on burning:
- Saturated hydrocarbons generally gives a clean flame while
unsaturated carbon compounds gives a yellow flame with lots of
black smoke.
Causes of giving sooty flame by saturated hydrocarbons:
Due to the limit supply of air results in incomplete combustion of even saturated hydrocarbons giving a sooty flame. The gas/kerosene stove used at home has inlets for air so that a sufficiently oxygen-rich mixture is burnt to give a clean blue flame.
The bottoms of cooking vessels getting blackened it means that
(i) The air holes are blocked
(ii) fuel is getting wasted.
Disadvantages of burning fuels such as coal and petroleum:
(i) The combustion of coal and petroleum results in the formation of oxides of sulphur and nitrogen which are major pollutants in the environment.
(ii) Incomplete combustion of coal and petroleum gives a sooty flame.
(iii) Incomplete combustion of coal and petroleum also gives carbon Monooxides which is dangerous poluutant.
Incomplete combustion of coal and petrolium:
(i) Incomplete combustion of coal and petroleum gives a sooty flame.
(ii) Incomplete combustion of coal and petroleum also gives carbon Monooxides which is dangerous poluutant.
Cause of some fuels burning without a flame:
The coal or charcoal in an ‘angithi’ sometimes just glows red and gives out heat without a flame. This is because a flame is only produced when gaseous substances burn. When wood or charcoal is ignited, the volatile substances present vapourise and burn with a flame in the beginning.
Why some substances burns with luminous flame:
A luminous flame is seen when the atoms of the gaseous substance are heated and start to glow. The colour produced by each element is a characteristic property of that element.
Formation of coal and petroleum:
Coal and petroleum have been formed from biomass which has been subjected to various biological and geological processes. Coal is the remains of trees, ferns, and other plants that lived millions of years ago. These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by layers of earth and rock. They slowly decayed into coal. Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains, turning them into oil and gas under the high pressures they were being subjected to.
Alcohol:
Ethanol (CH3CH2OH):
Ethanol is commonly called alcohol.
Physical Properties of Ethanol:
(i) Ethanol is a liquid at room temperature.
(ii) It is a good solvent.
(iii) Ethanol is also soluble in water in all proportions.
(iv) It has highly flammability.
Chemical properties of Ethanol:
(i) Combustion: Ethanol burns in oxygen to produce carbon dioxide and water.
(ii) Dehydration: Dehydration of ethanol is done by heating with concentrated sulfuric acid, which behave as a dehydrating agent.
(iii) Oxidation: oxidation can be made by using oxidising agent like acidified potassium dichromate or alkaline potassium permanganate.
(iv) Estrification: Ethanol can be reacted with carboxylic acid to form esters.
Uses of Ethanol:
(i) It is the active ingredient of all alcoholic drinks.
(ii) It is also used in medicines such as tincture iodine, cough syrups, and many tonics.
(iii) For synthesis of industrial methylated spirits.
(iv) Ethanol burns to give carbon dioxide and water and can be used as a fuel.
Harmful effects of drinking Alcohols/Ethanol:
(i) Consumption of small quantities of dilute ethanol causes drunkenness.
(ii) Short-term use of alcohol causes Slurred speech, drowsiness, vomiting and headache etc.
(iii) Long-term consumption of alcohol leads to many health problems such as alcohol poisioning, liver disease, nerve damage and permanent damage of brain etc.
(iv) It tends to slow metabolic processes and to depress the central nervous system. This results in lack of coordination, mental confusion, drowsiness, lowering of the normal inhibitions, and finally stupour.
(v) The individual may feel relaxed but does not realise that his sense of judgement, sense of timing, and muscular coordination have been seriously impaired.
(i) Reaction with Sodium: Alcohols react with sodium leading to the evolution of hydrogen and the other product is sodium ethoxide.
The equation is as follows:
2Na + 2CH3CH2OH → 2CH3CH2O–Na+ + H2
(sodium ethoxide)
(ii) Reaction to give unsaturated hydrocarbon: Heating ethanol at 443 K with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene –
Denatured Alcohol: To prevent the misuse of ethanol produced for industrial use, it is made unfit for drinking by adding poisonous substances like methanol to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.
Ethanoic Acid (CH3COOH):
Ethanoic acid is commonly called acetic acid and belongs to a group of acids called carboxylic acids.
- 5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles.
- The melting point of pure ethanoic acid is 290 K (17 oC) and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.
Properties:
(i) It has acidic nature.
(ii) Ethanoic acid is an odorless and highly smelling liquid.
(iii) Its melting point is 290 K.
Use of Ethanoic Acid/Acetic Acid:
Group is called carboxylic Acid:
The uses of ethanoic acid are followings:
(i) It is used as preservative for preparing pickes in the form of vinegar.
(ii) It is used as laboratory's agent.
(iii) Manufacturing of white led.
(iv) It is used in the manufactering of Reyon fibres.
(v) Acetic acid is used as coagulant in the manufacture of rubber.
(vi) It is used as a solvent.
Reactions of ethanoic acid:
(i) Esterification reaction: Esters are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester –
The reaction is as;
Ester: The reaction by ethanol and ethanoic acid resulting forms the compound that is called Ester. The molecular formula of ester is CH3COOCH2CH3.
Uses of Esters:
Esters are sweet-smelling substances, the uses of esters are following.
(i) These are used in making perfumes and as flavouring agents.
(ii) These are also used to make surfactants such as soap and detergents.
(iii) Some esters can be made into polymers called polyesters.
Esterification reaction: The reaction which gives Ester that is called estrification.
Saponification: Ester reacts in the presence of an acid or a base to give back the alcohol and carboxylic acid this reaction is known as saponification.
Because esters are used in preparation of soap.
Equation for saponification reaction:
(ii) Reaction with a base: Like mineral acids, ethanoic acid reacts with a base such as sodium hydroxide to give a salt (sodium ethanoate or commonly called sodium acetate) and water:
NaOH + CH3COOH → CH3COONa + H2O
(iii) Reaction with carbonates and hydrogencarbonates: Ethanoic acid reacts with carbonates and hydrogencarbonates to give rise to a salt, carbon dioxide and water. The salt produced is commonly called
sodium acetate.
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
Soap And Detergents
Chapter 4. Carbon and It's Compounds
Soap And Detergents:
Soaps: The molecules of soap are sodium or potassium salts of long-chain carboxylic acids. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules, thus form structures called micelles.
Micelles : When soap is at the surface of water, inside water these molecules have a unique orientation that keeps the hydrocarbon portion out of the water. This is achieved by forming clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle.
The Structure of Micelle
There are important roles of ends of soap molecules for formation of the structure of Micelle.
The Micelle has two ends:
(i) Hydrophilic end: The end which dissolves in water is called hydrophilic end.
(ii) Hydrophobic end: The end which dissolves in hydrocarbons (oily substances) is called hydrophobic end.
Differences between hydrophilic end and hydrophobic end :
Hydrophilic end:
(i) It dissolves in water.
(ii) This is ionic end.
(iii) The ionic ends are on the surface of the cluster.
Hydrophobic end:
(i) It dissolves in hydrocarbons.
(ii) This is not ionic end.
(iii) The hydrophobic tails are in the interior of the cluster.
The cleaning process of soap:
The cleaning process is characterised by soap micelle. The ionic end of soap is dissolves in water and other end dissolves in oily scum and thus forms structure of micelles. Thus micelles are able to clean as soap because oily scums gather in the center of micelles. There forms emulsion in the water. The micelles stay
in solution as a colloid and will not come together to precipitate because of ion-ion repulsion. Thus, the dirt suspended in the micelles is also easily removed away and our clothes are cleaned
Micelle properties:
(i) A micelle as soap is able to clean.
(ii) The micelles stay in solution as a colloid.
(iii) These are not precipitated due to ion-ion repulsion.
(iv) Soap micelle can disperse light.
(v) The micelles of soap help to dissolve oily scum in the water.
The soap does not form foam with hard water:
When we wash hand with soap in hard water, we see that foam formed with very difficulty and an insoluble substance (scum) remains after washing with
water. This is caused by the reaction of soap with the calcium and magnesium salts, which cause the hardness of water. Hence you need to use a larger amount of soap.
The detergent is more effective even in hard water:
Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water.
Differences between soap and detergent:
Soap:
(i) The molecules of soap are sodium or potassium salts of long-chain carboxylic acids.
(ii) It does not form foam in hard water.
(iii) It increases the hardeness of water.
(iv) It forms micelle during cleaning process.
Detergent:
(i) Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids.
(ii) It form foam even in hard water.
(iii) It increases the softness of water.
(iv) It does not form micelle during cleaning process.
Use of detergents:
(i) Detergents are usually used to make shampoos and products for cleaning clothes.
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Science Chapter List
1. Chemical Reactions and Equations
2. Acids, Bases and Salts
3. Metals and Non-metals
4. Carbon and its Compounds
5. Periodic Classification of Elements
6. Life Processes
7. Control and Coordination
8. How do Organisms Reproduce
9. Heredity and Evolution
10. Light-Reflection and Refraction
11. Human Eye and Colourful World
12. Electricity
13. Magnetic Effects of Electric Current
14. Sources of Energy
15. Our Environment
16. Management of Natural Resources
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