carbon & its compounds kolabari tutorial cbse x study

Carbon & its Compounds Kolabari Tutorial CBSE X Study material

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Carbon and its compounds

Allotropes of an element are the various forms in which that element can exist with widely varying

physical properties even though their chemical properties are the same. This phenomenon is called

allotropy. Three allotropes of carbon are Diamond, Graphite, and Buckminsterfullerene.

Diamond Graphite

Structure In diamond, each carbon atom is bonded to four other carbon atoms

forming a rigid three-dimensional

tetrahedral structure.

In graphite, each carbon atom is bonded to three

another carbon atoms in the same plane forming a

two-dimensional hexagonal arrays being

placed in layers one above the other.

Physical property

It is the hardest substance known and an bad conductor of electricity.

It is smooth and slippery and a very good conductor of electricity

Uses In making jewellery, drilling equipment and cutting instruments

In making lubricant, electrodes in dry cell and pencil leads

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.

The earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, hydrogen carbonates,

coal and petroleum) and the atmosphere has 0.03% of carbon dioxide.

All the living things, plants and animals, are made up of carbon based compounds which are called

organic compounds. These compounds were initially extracted from natural substances and it was thought

that these carbon compounds or organic compounds could only be formed within a living system. That is, it

was postulated that a ‘vital force’ was necessary for their synthesis.



Friedrich Wohler prepared the organic compound ‘urea” [CO(NH₂)₂] in the laboratory from

an inorganic compound ‘ammonium cyanate’ (NH₄CNO) in 1828.This led to the rejection of the vital

force theory for the synthesis of organic compound.

The compounds of carbon, other than oxides of carbon, carbonates, hydrogen carbonates and carbide

are called organic compounds.

A large number of things which we use in our daily life are made of carbon compounds; such as our food

(grains, pulses, tea..), cloth material(cotton, silk, nylon...), fuels( LPG - Liquefied Petroleum Gas, CNG –

Compressed natural gas, kerosene,...), rubber, plastics, leather, drugs and dyes etc. In fact, we ourselves are

made up of carbon compounds. We can test the presence of carbon in a material on the basis of the

fact that carbon and its compounds burn in air to give carbon dioxide gas which turns lime water milky.

The following two characteristic features enable carbon to form a large number of compounds:

(i) Carbon has the unique ability to form bonds with other atoms of carbon. This property is called

catenation. These compounds may have long chains of carbon, branched chains of carbon or even

carbon atoms arranged in rings. In addition, carbon atoms may be linked by single, double or triple

bonds.

(ii) Since carbon has tetravalency (i.e. valency of four), it is capable of bonding with four other atoms of

carbon or atoms of some other mono-valent element. One more reason for 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 the sharing of electrons are known as covalent bonds. If each atom contribute

one electron, the covalent bond formed is called a single covalent bond and is represented by a single line (–);

If each atom contribute two electrons, the covalent bond formed is called a double covalent bond and is

represented by a double line ( ꞊ ) and If each atom contribute three electrons, the covalent bond formed is

called a triple covalent bond and is represented by a triple line ( ≡ ).

Carbon always forms covalent bonds as it contains four electrons in its valence shell and it is difficult for

it to lose or gain four electrons in order to complete its octet.

Covalently bonded molecules are seen to have strong bonds within the molecule, but intermolecular

forces are small. This gives rise to the low melting and boiling points of these compounds.

Since the electrons are shared between atoms and no charged particles are formed, such covalent

compounds are generally poor conductors of electricity.

Lewis electron dot structure of bond formation of some covalent compounds:



Properties of Covalent Compounds : The covalent compounds do not exist as ions but they exist as

molecules. They exist at room temperature, as liquids or gases. However, a few compounds also exist in the

solid state e.g. urea, sugar, etc. The melting and boiling points of covalent compounds are generally low.

Covalent compounds are generally insoluble or less soluble in water and in other polar solvents. These are

poor conductors of electricity in the fused or dissolved state

All the carbon compounds which contain just carbon and hydrogen are called hydrocarbons.

The compound of carbon, which are linked by only single bonds between the carbon atoms are called

saturated hydrocarbons. The saturated hydrocarbons are called alkanes (general formulae –

).

Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated

hydrocarbons. The unsaturated hydrocarbons which contain one or more double bonds are called

alkenes ( ). Those unsaturated hydrocarbons containing one or more triple bonds are called

alkynes ( ).

Hydrocarbons in which the carbon atoms are arranged in the form of a ring, such hydrocarbons are

called cyclic hydrocarbons. Cyclohexane (C₆H₁₂) is an example of saturated cyclic hydrocarbon

whereas benzene (C₆H₆) is an unsaturated cyclic hydrocarbon.

In an organic compound, any atom other than carbon and hydrogen is called a heteroatom.

A homologous series is a group of organic compounds having similar structures and similar chemical

properties in which the successive compounds differ by CH₂ group. Ex: alkanes, alkenes, alkynes,

haloalkanes, alcohols, aldehydes, ketones and carboxylic acids.

The difference in the molecular masses of two adjacent homologues is 14u. As the molecular mass increases

in any homologous series, a gradual change in their 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.

An atom or a group of atoms which makes a carbon compound reactive and decides its properties is

called a functional group.

The group formed by the removal of one hydrogen atom from an alkane molecule is called an alkyl

group. The general formula of an alkyl group is .

When one hydrogen atom of an alkane is replaced by a halogen atom, we get haloalkane. The hydroxyl

group(-OH) attached to a carbon atom is known as alcohol group. Other functional groups are aldehyde

group (-CHO), ketone group (>C=O), carboxylic acid group (-COOH)



The compounds with identical molecular formula but different structures are called isomers, and this

phenomenon is known as isomerism. Example:

isomers of Butane (C₄H₁₀):

isomers of Pentane(C₅H₁₂):

Butane, pentane and hexane have 2, 3 and 5 possible isomers respectively.

IUPAC Name: The official names or systematic names of organic compounds were given by

International Union of Pure and Applied Chemistry in 1958. So they are called IUPAC name or IUPAC

nomenclature. Naming a carbon compound can be done by the following method:

(i) The longest continuous chain of ‘C’ atoms, known as parent chain, is selected. Number of ‘C’atoms

present in it determines root word of its name.

No. of C-atoms 1 2 3 4 5 6

Root word Meth Eth Prop But Pent Hex

(ii) The root word is followed by one appropriate suffix, which represents the nature of bond in carbon-

carbon atom.

Nature of bond Suffix General name General formula

Single bond (C-C) -ane Alkane

Double bond (C=C) -ene Alkene

Triple bond (C≡C) -yne Alkyne

(iii) The branch chains are considered to be substituents, and their positions are indicated by the number of

carbon atoms to which they are attached.

(iv) The carbon atoms of the largest chains are numbered in such a way that the alkyl group get the smallest

possible number.

(v) In case, any functional group is also present in the chain, then the carbon atoms are numbered in such a

way that the functional group gets the smallest possible number.

(vi) In nomenclature, ‘e’ of alkane is replaced by suffix of functional group indicating position.

(vii) The position(s) of alkyl group(s) are indicated by writing the position and name of the alkyl group just

before the name of parent hydrocarbon.

(viii) Di-, tri-, tetra-, are used as prefix for two, three and four groups of the same type.



Functional group General formulae Types of organic compounds Suffix Preffix

Halide – X (Cl,Br, F,I) R– X Haloalkanes Chloro, bromo..

Hydroxyl – OH R– OH Alcohols ol Aldehyde –CHO

Aldehydes al

Carboxyl –COOH

Carboxylic acid oic acid

Keto

Ketones one

Ether R–O– Rʹ Ethers oxy

Methane [CH₄]

Ethane [C₂H₆]

Propane [C₃H₈]

Butane [C₄H₁₀] (n-butane)

2-methyl propane [C₄H₁₀] (Iso butane)

Ethene [C₂H₄](Ethylene)

Propene /prop-1-ene [C₃H₆](Propylene)

Butene/but-1-ene [C₄H₈] (Butylene)

But-2-ene [C₄H₈]

2-methylpropene [C₄H₈]

Ethyne [C₂H₂]

Propyne [C₃H₄] (Acetylene)

But-2-yne [C₄H₆]

Methanol/Methan-1-ol [CH₃OH]

Ethanol [C₂H₅OH]

Propanol/Propan-1-ol [C₃H₇OH]

Propanol/Propan-2-ol [C₃H₇OH]

propan-1,2,3-triol [C₃H₅(OH)₃] (Glycerol)

Methanal/Methan-1-al [CH₂O](Formaldehyde)

Propanal/Propan-1-al [C₂H₄O](Acetaldehyde)

Propan-2-one [C₃H₆O] (Acetone)

Methanoic-1-oic acid [CH₂O₂] (Formic acid)

Ethanoic acid [C₂H₄O₂] (Acetic acid)

Ethyl ethanoate [C₄H₈O₂](Ethyl acetate)

Chloromethane [CH₃Cl]

1,2-dibromopropane [C₃H₆Br₂]

Trichloromethane [CHCl₃]

Tetrachloromethane [CCl₄] (Chloroform) (Carbon tetrachloride)

Cyclohexa-1,3,5-triene[C₆H₆](Benzene)

Cyclo propane [C₃H₆]



A fuel is a material that has energy stored inside it. When a fuel is burned, the energy is released mainly

as heat. Coal, petroleum and natural gas are known as fossil fuels because they were formed by the

decomposition of the remains of the prehistoric plants and animals (fossils) buried under the earth, long,

long, ago.

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 complex mixture of compounds of carbon, hydrogen and oxygen, and some free carbon. Coal is

formed by the decomposition of large land plants and trees buried under the earth millions of years

ago.

Petroleum means rock oil (petra oleum). It is found under the crust of earth trapped in rocks.

Petroleum oil and natural gas were formed by the decomposition of the remains of extremely small

plants and animals buried under the sea millions of years ago.

The crude oil petroleum is a complex mixture of several solid, liquid and gaseous hydrocarbons mixed with

water, salt and earth particles. Small amounts of nitrogen and sulphur compounds are also present in coal

and petroleum. So when these fuels are burnt, they lead to the formation of oxides of nitrogen and sulphur

which are major air pollutants.

A flame is the region where combustion (or burning) of gaseous substance takes place. If the oxygen

supply (or air supply) is sufficient, then the fuels burn completely producing a blue flame. And if oxygen

supply is insufficient, then the fuel burn incompletely producing mainly a yellow flame. Blue flame is said to

be non luminous (not produce much light). And yellow flame is said to be luminous (light giving) flame.

All the gaseous fuels burn with a flame but only those solid and liquid fuels which

vaporise on heating (to form a gas), burn with a flame. LPG (gas) and wax candle (solid) burns

with blue and yellow flame whereas coal or charcoal in an ‘angithi’ sometimes just glows red (burns

without producing a flame) 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.

Chemical properties of carbon compounds

1.Combustion: The process of burning of a carbon compound in air to give carbon dioxide, water, heat and

light, is known as combustion.

CH₄ + 2O₂ CO₂ + 2H₂O + Heat + Light

Incomplete combustion results formation of pollutant such as carbon monoxide (extremely poisonous)

and unburnt carbon (soot).



The saturated hydrocarbons generally burn in air with a blue, non-sooty flame [Ex –

Camphor and alcohol]. And the unsaturated hydrocarbons burn in air with a yellow, sooty

flame [Ex - naphthalene]. This is because the percentage of carbon in the saturated hydrocarbons is

comparatively low which gets oxidised completely by the oxygen present in air.

If unsaturated hydrocarbons are burned in pure oxygen, then they will burn completely producing a blue

flame. However, if the supply of air for burning is reduced, then incomplete combustion of even saturated

hydrocarbon will take place and they will burn producing a sooty flame.

The gas stove has tiny holes for air so that sufficient oxygen of air is available for the complete burning of

fuel to produce a smokeless blue flame. So, if the bottoms of the cooking utensils are getting blackened, it

shows that the air holes of the gas stove are getting blocked and the fuel is not burning completely.

Acetylene burns in air with a very sooty flame due to incomplete combustion, which is not hot enough. If

a mixture of acetylene (ethyne) and pure oxygen is burned, then acetylene burns completely producing

enough heat to melt metals for welding. So, Oxy-acetylene torch being used for welding metals.

2. Substitution reactions: Saturated hydrocarbons are fairly nonreactive and are inert in the

presence of most reagents. However, in the presence of sunlight, chlorine is added to hydrocarbons in a

very fast reaction. Chlorine can replace the hydrogen atoms one by one.

The reaction in which one (or more) hydrogen atoms of hydrocarbon are replaced by some other atoms

(like chlorine), is called a substitution reaction.

Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride:

CH₄ + Cl₂ CH₃Cl + HCl ; CH₃Cl + Cl₂

CH₂Cl₂ + HCl

CH₂Cl₂ + Cl₂ CHCl₃ + HCl ; CHCl₃ + Cl₂

CCl₄ + HCl

By supplying more chlorine, it is possible to replace all the hydrogen atoms of methane by chlorine, one

by one. In this way we can obtain three more compounds: Dichloromethane(CH₂Cl₂); Trichlromethane or

Chloroform (CHCl₃); and Tetrachloromethane (CCl₄).

Substitution reactions are a characteristic property of saturated hydrocarbons or alkanes.

3. Addition reactions: The reaction in which an unsaturated hydrocarbon combines with another

substance to give a single product is called an addition reaction.

Addition reactions are a characteristic property of unsaturated hydrocarbon. Ethene reacts with

hydrogen when heated in the presence of nickel catalyst to form ethane:



Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to

give saturated hydrocarbons. This process is known as hydrogenation and commonly used to prepare

vegetable ghee from the hydrogenation of vegetable oils (industrial use).

Vegetable oils generally have long unsaturated carbon chains while animal fats have

saturated carbon chains. The vegetable oils containing unsaturated fatty acids should be chosen for

cooking, they are ‘healthy’. The saturated fats like vegetable ghee, obtained by the hydrogenation of oil, are

not good for health. Animal fats also contain saturated fatty acids which are said to be harmful for health.

Test: All the unsaturated compounds decolourise red-brown bromine water (bromine gets

added to unsaturated compound and looses its colour) but saturated compounds do not

decolourise bromine water. We can distinguish chemically between a cooking oil and butter by the

bromine water test. Cooking oil (unsaturated compound) decolourise bromine water but Butter (saturated

compound) does not decolourise it.

Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction

itself being affected.

Some important carbon compounds:

1. Ethanol (or Ethyl alcohol): Ethanol is a colourless liquid at room temperature. The melting point of

ethanol is 78°C (351 K). Ethanol is a good solvent and due to presence of hydroxyl group it is also soluble in

water in all proportions. Sugarcane plants are one of the most efficient convertors of sunlight into chemical

energy. Sugarcane juice can be used to prepare molasses which is fermented to give alcohol (ethanol).

Ethanol containing 5% water is called rectified spirit (commercial alcohol).

Chemical property:

Combustion: Ethanol burns readily in air to form carbon dioxide and water vapour, and releasing a lot

of heat and light.

C₂H₅OH + 3O₂ 2CO₂ + 3H₂O + Heat + Light



Reaction with sodium: Alcohols react with sodium leading to the evolution of hydrogen. With

ethanol, the other product is sodium ethoxide.

2C₂H₅OH + 2Na 2C₂H₅O¯Na⁺ + H₂

(sodium ethoxide)

On dropping a small piece of sodium, about the size of a couple of grains of rice, into ethanol (absolute

alcohol) a brisk effervescence produced due to formation of hydrogen gas. This gas can be checked by

bringing burning splinter near it which starts burning with pop sound. It confirms that evolve gas is H₂

gas.

Reaction to give unsaturated hydrocarbon (Dehydration): Heating ethanol at 443 K with excess

concentrated sulphuric acid results in the dehydration of ethanol to give ethene.

CH₃CH₂OH CH₂ = CH₂ + H₂O

The conc. sulphuric acid can be regarded as a dehydrating agent which removes water from ethanol.

Alcohols get converted to carboxylic acids on oxidation:

CH₃CH₂OH + 2[O] CH₃COOH + H₂O

Alkaline potassium permanganate or acidified potassium dichromate are oxidising alcohols to acids, that

is, adding oxygen to the starting material. Hence they are known as oxidising agents.

When we take about 3 mL of ethanol in a test tube and warm it gently in a water bath and add a 5%

solution of alkaline potassium permanganate drop by drop to this solution. The colour of potassium

permanganate disappears initially because it oxidises ethanol to ethanoic acid and itself reduced to

manganese dioxide (MnO₂). However the colour of potassium permanganate does not disappear when

excess is added because some of the KMnO₄ solution (extra) remains unused.

Esterification reaction: Absolute ethanol reacts with ethanoic acid in the presence of a few drops

of concentrated sulphuric acid (as catalyst) to give an ester –

CH₃COOH + C₂H₅OH CH₃COOC₂H₅ + H₂O

Ethanoic acid Ethanol (Ethyl ethanoate / ester)

Esters are sweet-smelling substances. These are used in making perfumes and as flavouring agents.

Tests:

Sodium metal test: We add a small piece of sodium metal to the organic liquid (to be used), taken in

a dry test-tube. If bubbles of hydrogen gas are produced, it indicates that the given organic liquid is an

alcohol.

Ester test for Alcohol: The organic compound (to be tested) is warmed with some glacial ethanoic

acid and a few drops of concentrated sulphuric acid. A sweet smell ( due to the formation of ester)

indicates that the organic compound is an alcohol.

Uses:

Ethanol is commonly called alcohol and is the active ingredient of all alcoholic drinks.

Ethanol is used in the manufacture of paints, varnishes, perfumes, dyes, soaps and synthetic rubber.



In addition, because it is a good solvent, it is also used in medicines such as tincture iodine, cough

syrups, and many tonics.

Some countries now use alcohol as an additive in petrol since it is a cleaner fuel.

Ethanol is an important industrial solvent. To prevent the misuse of ethanol produced for industrial use,

it is made unfit for drinking by adding poisonous substances like methanol and pyridine to it. Dyes

like copper sulphate are also added in small amount to colour the alcohol blue so that it can be

identified easily. This is called denatured alcohol.

Harmful effect: When large quantities of ethanol are consumed, 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. The individual may feel relaxed but does not realise that his sense of

judgement, sense of timing, and muscular coordination have been seriously impaired. Unlike ethanol, intake

of methanol in very small quantities can cause death. Methanol is oxidised to methanal in the liver. Methanal

reacts rapidly with the components of cells. It causes the protoplasm to get coagulated, in much the same

way an egg is coagulated by cooking. Methanol also affects the optic nerve, causing blindness.

2. Ethanoic acid (or Acetic acid): 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 and hence it often freezes

during winter in cold climates. This gave rise to its name glacial acetic acid.

The group of organic compounds called carboxylic acids are obviously characterised by a special acidity.

However, unlike mineral acids like HCl, carboxylic acids are weak acids.

Chemical property

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:

CH₃COOH + NaOH CH₃COO¯Na⁺ + H₂O

(Sodium ethanoate)

Reaction with carbonates and hydrogencarbonates: Ethanoic acid reacts with carbonates and

hydrogen carbonates to give rise to a salt sodium ethanoate, carbon dioxide and water.

2CH₃COOH + Na₂CO₃ 2CH₃COO¯Na⁺ + CO₂ + H₂O

CH₃COOH + NaHCO₃ CH₃COONa + CO₂ + H₂O

When we take a spatula full of sodium carbonate in a test tube and add 2 mL of dilute ethanoic acid, a

brisk effervescence produced due to evolution of CO₂ gas. When this gas passes through freshly prepare

lime water, it turns milky. Same observation is made when sodium bicarbonate (sodium hydrogen

carbonate) is used instead of sodium carbonate.

Tests:



Sodium hydrogen carbonate test: The organic compound (to be tested) is taken in a test tube and a

pinch of sodium hydrogen carbonate is added to it. Evolution of CO2 gas with brisk effervescence

shows that organic compound is a carboxylic acid.

Ester test for acids: The organic compound (to be tested) is warmed with some ethanol and a few

drops of concentrated sulphuric acid. A sweet smell (due to the formation of ester) indicates that the

organic compound is a carboxylic acid.

Hydrolysis of Esters: When an ester is heated with sodium hydroxide solution then the ester gets

hydrolysed (breaks down) to form the parent alcohol and sodium salt of the carboxylic acid. For example,

when ethyl ethanoate ester is boiled with sodium hydroxide solution, then sodium ethanoate and ethanol are

produced:

CH₃COOC₂H₅ + NaOH CH₃COONa + C₂H₅OH

This reaction (alkaline hydrolysis of esters) is known as saponification reaction. This is because

this reaction is used for the preparation of soaps.

Soaps and Detergent

1. Soaps : Soaps are sodium or potassium salts of long chain acid carboxylic acids which has a cleansing

effect in water. Ex- Sodium stearate (C₁₇H₃₅COO¯Na⁺) and Sodium palmitate (C₁₅H₃₁COO¯Na⁺)

A soap is the salt of a strong base (sodium hydroxide) and weak acid (carboxylic acid), so a solution of

soap in water is basic in nature.

Soap is made by heating animal fat or vegetable oil with concentrated sodium hydroxide solution. The

fats or oils react with sodium hydroxide to form soap and glycerol:

Fat or oil + sodium hydroxide Soap + Glycerol

(An ester) (An alkali) (Sodium salt of fatty cid) (An alcohol)

The process of making Soap by the hydrolysis of fats and oils with alkalis is called saponification.

Common salt is added in soap making to precipitate out all the soap from the aqueous solution.

Structure of a soap molecule: A soap molecule is made up of two parts - a long hydrocarbon part

and a short ionic part containing –COO¯Na⁺ group. A soap molecule is said to have a tadpole structure. Its

long hydrocarbon part of soap is hydrophobic (water-repelling), and its ionic portion is hydrophilic

(water-attracting).



Cleansing action: When soap is dissolved in water, it forms colloidal suspension in water in which the

soap molecule cluster together and form a sphere such that hydrocarbon ends directed towards the centre

and ionic ends directed outwards. A ‘spherical aggregate of soap molecules’ in the soap

solution in water is called a ‘micelle’.

When dirty cloth is put in water containing dissolved soap, then the hydrocarbon ends of the soap

molecules in the micelle attach to the oil or grease particles present on the surface of dry cloth. The ionic

ends of soap molecules in micelles however remain attached to water. In this way the soap micelle entraps

the oily particle and when the dirty cloth is agitated in soap solution, these entrapped oily and greasy

particles dispersed in water .The cloth is cleaned thoroughly by rinsing in clean water number of times.

Limitation: Soap is not suitable for washing clothes with hard water because of two reasons: (i) A large

amount of soap is wasted in reacting with the calcium and magnesium ions of hard water to form an

insoluble precipitate called scum, so it does not form lather or foam (necessary for removing dirt) easily with

hard water. (ii) The scum formed by the action of hard water on soap, sticks to the clothes being washed and

interferes with the cleansing ability of the additional soap.

2. Detergent: A detergent is the sodium salt of a long chain benzene sulphonic acid which has cleansing

property in water. Ex- Sodium n-dodecyl benzene sulphonate [CH₃-(CH₂)₁₂ - C₆H₄-SO₃¯Na⁺]

Detergents are better cleansing agents than soaps because they do not form insoluble calcium and

magnesium salts with hard water, and hence can be used for washing even with hard water. The cleansing

action of detergent is similar to that of soap. They are usually used for make washing powders and shampoos.

An important disadvantage of detergents over soaps is that some of the detergents are not

biodegradable and hence cause water pollution in lakes and rivers.

Miscellaneous:

The unsaturated hydrocarbons are obtained mostly from petroleum by a process called cracking.



Ethene is used for ripening many raw fruits and Polythene is made up by polymerisation of ethene.

Iso butane is used in cooking gas LPG (Liquid petroleum Gas).

Methanal or formaldehyde is used in making plastic for plugs and sockets, a solution of formaldehyde in

water(called formalin) is used to preserve biological specimens.

Propanone (or acetone) is a very good solvent for nail polish, so it is used as nail polish remover.

Compound Ethene Ethyne Ethanol Methanal Ethanal Propanone Methanoic acid

Ethanoic acid Ethyl ethanoate

Common

name

Ethylene Acetylene

Ethyl alcohol

Formaldehyde

Acetaldehyde

Acetone

Formic acid

Acetic acid

Ethyl acetate or, ester

Self Assessment Work Sheet

Q1. What is the difference in the molecular formula of any two consecutive members of a homologous series of organic

compounds?

Q2. Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene.

Q3. Name the compound formed when ethanol is warmed with ethanoic acid in the presence of a few drops of

cone.H₂S0₄

Q4. What happens when a small piece of sodium is dropped into ethanol?

Q5. State two characteristic features of carbon which when put together give rise to large number of carbon

compounds.

Q6. How many covalent bonds are there in a molecule of ethane (C₂H₆)?

Q7. Name the functional group present in CH₃COCH₃

Q8. Write the name and formula of the second member of the carbon compounds having functional group —OH.

Q9. Write the name and formula of the first member of the carbon compounds having following functional group [a] —

CHO. [b] —COOH.

Q10. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is

OH

Q11. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula

is

Q12. Why are covalent compounds generally poor conductors of electricity?

Q13. Name the oxidising agent used for the conversion of ethanol to ethanoic acid.

Q14. Why ethanoic acid is called glacial acetic acid?



Q15. Name the functional group present in each of the following organic compounds: [a] C₂H₅CI [b] HCOOH [c]

Butanone [d] C₂H₅CHO

Q16. Draw the structure of following molecule:[a] butanone [b] hexanal [c] ethanol [d] Chloroethane

Q17. [a] Give a chemical test to distinguish between saturated and unsaturated hydrocarbons. [b] (i) Name the products

formed when ethanol burns in air. (ii) What two forms of energy are liberated on burning alcohol? [c] Why is the

reaction between methane and chlorine considered a substitution reaction?

Q18. Explain why carbon generally forms compounds by covalent bonds.

Q19. Write the names and molecular formula of two organic compounds having functional group suffixed as ‘-oic acid’.

With the help of a balanced chemical equation and explain what happens when any one of them reacts with sodium

hydroxide.

Q20. Atom of an element contains five electrons in its valence shell. This element is major component of air. It exists as

a diatomic molecule. [a] Identify the element. [b] Show the bond formed between two atoms of this element. [c] Write

the nature of the bond between the two atoms.

Q21. Which two of the following organic compounds belong to the same homologous? CH₃ ,C₂H₆, C₂H₆O, C₂H₆O₂,CH₄O

Q22. [a] What is meant by a functional group in an organic compound? Name the functional group present in CH₃CH₂OH

[b] State one point of difference between soap and synthetic detergent.

Q23. Write IUPAC names of [a] CH₃—CH₂—CH=CH₂ [b] CH₃CHO [c] CH₃COCH₂CH₃ [d] HCOOH

[e] CH₃COOCH₃ [f] [g] [h]

Q24. Give reasons for the following observations: [a] Air holes of a gas burner have to be adjusted when the heated

vessels get blackened the flame. [b] Use of synthetic detergents causes pollution of water.

Q25. What is ethanoic acid? What special name is given to its 5 – 8% solution in water? How does ethanoic acid react

with sodium carbonate? Write a chemical equation of the reaction and common name of the salt produced.

Q26. An ester has the molecular formula C₄H₈O₂. Write its structural formula. What is a saponification reaction?

Q27. Out of HCI and CH₃COOH, which one is a weak acid and why? Describe an activity to support your answer.

Q28. With the help of suitable example explain the process of hydrogenation mentioning the conditions of the reaction

and any one change in physical property with the formation of the product. Name any one natural source of organic

compounds that are hydrogenated.

Q29. An organic compound ‘A’ is an essential constituent of wine and beer. Oxidation of ‘A’ yields an organic acid ‘B’

which is present in vinegar. Name the compounds ‘A’ and ‘B’ and write their structural formula. What happens when

‘A’ and ‘B’ react in the presence of an acid catalyst? Write the chemical equation for the reaction.



Q30. [a] What is ethanol? State its two properties. [b] What happens when it is heated with excess of conc. H₂SO₄ at 443

K? [c] What role does cone. H₂SO₄ play in this reaction? Write chemical equation of the reaction involved and the

structural formula of the main product formed.

Q31. What is an ‘esterification’ reaction? Describe an activity to show esterification.

Q32. Write a chemical equation in each case to represent the following types of chemical reactions of organic

compounds: [a] Oxidation reactions [b] Addition reactions [c] Substitution reactions

Q33. Write chemical equations for what happens when [a] sodium metal is added to ethanoic acid. [b] solid sodium

carbonate is added to ethanoic acid. [c] ethanoic acid reacts with a dilute solution of sodium hydroxide.

Q34. What are isomers? Draw the structures of two isomers of butane, C₄H₁₀. Why can’t we have isomers of first three

members of alkane series?

Q35. Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the

first member of the series of alkenes.

Q36. Why homologous series of carbon compounds are so called? Write chemical formula of two consecutive members

of a homologous series and state the part of these compounds that determines their [a] physical properties, and [b]

chemical properties.

Q37. What are esters? How are they prepared? List two uses of esters.

Q38. List two tests for experimentally distinguishing between an alcohol and a carboxylic acid and describe how these

tests are performed.

Q39. Why does micelle formation take place when soap is added to water? Why are micelles not formed when soap is

added to ethanol?

Q40. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the

reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions.

Q41. What are micelles? Why does it form when soap is added to water? Will a micelle be formed in other solvents such

as ethanol also? State briefly how the formation of micelles helps to clean the clothes having oily spots.

Q42. [a] State any four characteristics of isomers. [b]In tabular form, differentiate between ethanol and ethanoic acid

under the following heads: (i) Physical state (ii) Taste (iii) NaHCO₃ test (iV) Ester test

Q43. Give reasons for the following: [a] Element carbon forms compounds mainly by covalent bonding. [b] Diamond has

a high melting point. [c] Graphite is a good conductor of electricity. [d] Acetylene burns with a sooty flame. [e]Kerosene

does not decolourise bromine water while cooking oils do.

Q44. What is the difference between the chemical composition of soaps and detergents? State in brief the action of

soaps in removing an oily spot from a shirt. Why are soaps not considered suitable for washing where water is hard?

carbon & its compounds kolabari tutorial cbse x study

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