RBSE Class 10 Science Important Questions Chapter 4 Carbon and Its Compounds

Rajasthan Board RBSE Class 10 Science Important Questions Chapter 4 Carbon and Its Compounds Important Questions and Answers.

RBSE Class 10 Science Chapter 4 Important Questions Carbon and Its Compounds

Objective Type Questions

Question 1.
The allotrop of carbon in which free electrons are present is –
(a) Diamond
(b) Coal
(c) Graphite
(d) Coke
Answer:
(c) Graphite

Question 2.
The side product in the process of soap formation is –
(a) NaOH
(b) Glycerol
(c) Fatty acid
(d) Alcohol
Answer:
(b) Glycerol

Question 3.
Total number of bonds present in Ethylene (Ethene) are –
(a) 5
(b) 6
(c) 4
(d) 7
Answer:
(b) 6

Question 4.
The compound formed by the Hydration of Ethene is—
(a) C₂H₆
(b) C₂H₅OH
(c) C₂H₂
(d) CH₃-CHO
Answer:
(b) C₂H₅OH

Question 5.
The formation of Acetic acid from Ethanol is –
(a) Reduction
(b) Oxidation
(c) Addition
(d) Substitution
Answer:
(b) Oxidation

Question 6.
Higher Homologue of butane is –
(a) Propane
(b) Pentane
(c) Pentene
(d) Ethyne
Answer:
(b) Pentane

Question 7.
IUPAC name of Acetone (CH₃COCH₃) is –
(a) Ethanal
(b) Propanone
(c) Ethanol
(d) Ethanoic acid
Answer:
(b) Propanone

Question 8.
IUPAC name of CH₃-CH₂COOH is –
(a) Methanoic acid
(b) Propanol
(c) Popanoic acid
(d) Propanal
Answer:
(c) Popanoic acid

Question 9.
Generally detergents are –
(a) RCOO Na
(b) R COOK
(c) RSO₄Na
(d) RCOOR
Answer:
(c) RSO₄Na

Very Short Answer Type Questions

Question 1.
Write the balanced equation of combustion of methane.
Answer:
The balanced equation of combustion of methane is as under –
CH₄+ 2O₂ → CO₂ + 2H₂O
(Methane) (Oxygen) (Carbon dioxide) (Water) + Heat and Light

Question 2.
What is the general formula of Alkenes?
Answer:
The general formula of Alkenes is C_nH_2n

Question 3.
What is ‘fullerenes’?
Answer:
Fullerenes are carbon allotropes in which the carbon atoms are arranged in the shape of a football.

Question 4.
What is the electron dot structure of methane (CH₄)?
Ans. The electron dot structure of methane is as under –

Question 5.
Write the name and chemical formula of organic acid present in Vinegar.
Answer:
organic acid present in vinegar is acetic acid, chemical formula of which is
CH₃COOH.

Question 6.
Write the two uses of Ethanoic acid.
Answer:

To make ester, vinegar.
In the preparation of soap.

Question 7.
Name the following compounds

Answer:

CH₃ – CH = CH₂ Propene (Propylene)
CH₃ – CH = O Ethanal (Acetaldehyde)

Question 8.
Write the name of compound CH₃COOH and identify the functional group of it.
Answer:
The name of compound CH₃ COOH is Acetic acid (Ethanoic acid) and its functional group is -COOH (Carboxylic acid)

Question 9.
Give the name of following compounds –
1. A alcohol derived from ethane
2. A ketone derived from butane
3. A carboxylic acid derived from methane.
Answer:

• Ethanol
• Butanone
• Methanoic acid.

Question 10.
A organic compound bums with sooty flame, then this compound is saturated or unsaturated?
Answer:
Unsaturated.

Question 11.
Write the name of functional group -COOH.
Answer:
Carboxylic acid group.

Question 12.
Write the structure of butanone.
Answer:

Question 13.
Covalent compounds are weak conductor of electricity, why?
Answer:
Free ions or electrons which are essential for conduction of electricity are not present in covalent compounds so these are weak conductor of electricity.

Question 14.
Which type of oils should be used for the cooking of food?
Answer:
Oils containing unsaturated fatty acids should be used for the cooking of food.

Question 15.
Write the complete name of CNG.
Answer:
The complete name of CNG is Compressed Natural Gas.

Quiestion 16.
Why coal and petroleum are called fossil fuels ? .
Answer:
Coal and petroleum have been formed from biomass, therefore they are called fossil fuels.

Question 17.
Give the uses of esters.
Answer:
Generally, esters are sweet smelling substances so these are used in making perfumes and as flavouring agents.

Question 18.
What is the geometry of carbon atom.
Answer:
The geometry of carbon atom is tetrahedral.

Question 19.
What is the general formula of Alkyne series?
Anwer:
The General formula of alkyne series is C_nH_{2n_2}.

Question 20.
Which type of compounds are present in detergents?
Answer:
Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids.

Question 21.
Write the full form of IUPAC.
Answer:
IUPAC = International Union of Pure and Applied Chemistry.

Question 22.
What will the formula of methyl acetylene?
Answer:
The formula of methyl acetylene is CH₃—C = CH. This is called Propyne.

Question 23.
What are soaps?
Answer:
The soaps are sodium (RCOONa) or potassium (RCOOK) salt of long chain carboxylic acids.

Question 24.
What is covalent bond?
Answer:
The bond formed by the sharing of one electron pair between two atoms is called covalent bond. This is very strong bond.

Question 25.
Write the name of first 6 members of Alkane series.
Answer:
Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈), Butane (C₄H₁₀), Pentane (C₅H₁₂) and Hexane (C₆H₁₄) are starting 6 members of Alkane series.

Question 26.
What is Hetero atom?
Answer:
The element which replace one or more hydrogen atoms in a hydrocarbon chain is called hetero atom. Example halogen (F, Cl, Br, I), oxygen, nitrogen and sulphur.

Question 27.
What is suffix of functional group Ketone?
Answer:
The suffix of ketone (>C = O) is -one.

Question 28.
What is oxidising agent?
Answer:
The substance which oxidise the other substance and itself is reduced, is called oxidising agent. This substance give oxygen for oxidation.

Question 29.
What is catalyst?
Answer:
The substance that change the rate of reaction but itself will not participate in the reaction is called catalyst.

Question 30.
Which compound is called alcohol?
Answer:
Generally, ethanol (C₂H₅OH) is called alcohol. This is important ingredient of all alcoholic drinks.

Question 31.
What is the valency of carbon ?
Answer:
Carbon is tetravalent because it was four valence electrons.

Question 32.
Why is carbon called a very friendly element ?
Answer:
Carbon easily forms covalent bonds with other carbon atoms as well as with hydrogen, halogen, oxygen, nitrogen and sulphur, hence, it is called a very friendly element.

Question 33.
Why do gas/kerosene stove used is homes have holes ?
Ansswer:
The gas/kerosene stove used at home has inlets for air so that a sufficient oxygen rich mixture is burnt to give a clean blue flame.

Question 34.
What will happen if saturated hydrocarbons are bum with limited supply of air ?
Answer:
Burning saturated hydrocarbons in limiting supply of air results in incomplete combustion giving a sooty flame.

Question 35.
What are the important uses of ethanol?
Answer:
Ethanol is a good solvent so it is used in medicines such as tincture iodine, cough syrups and many tonics.

Question 36.
Write the equation of reaction of acetic acid with NaOH.
Answer:

Question 37.
What is the IUPAC name of C₄H₉OH?
Answer:
The IUPAC name of C₄H₉OH is butanol.

Question 38.
Why the pure acetic acid is called glacial acetic acid?
Answer:
The melting point of pure acetic acid is 290 K hence it often freezes during winter in cold climates so this is called glacial acetic acid.

Question 39.
What is hydrocarbon?
Answer:
The organic compounds which have only carbon and hydrogen are called hydro-carbon.

Question 40.
Write the types of carbon chains?
Answer:
In the carbon compounds, carbon chains are straight, branched or in the forms of rings. These compounds may be saturated or unsaturated.

Question 41.
Who prepare the urea from ammonium cyanate, first time?
Answer:
Fredrich Wholar (1828) have prepared the urea from ammonium cyanate, first time.

Question 42.
What are Alkane, Alkene and Alkyne?
Answer:
Saturated hydrocarbons (C – C) are called Alkanes and unsaturated hydro-carbons having (C = C) and (C = C) are called Alkenes and Alkynes successively.

Question 43.
Carbon compounds are bad conductor of electrictiy and melting point and boiling point of these is low, why?
Answer:
Ions are not present in carbon compounds so attraction between molecules is weak hence these are bad conductor of electricity with low melting point and boiling point.

Question 44.
What is the use of methane (CH₄)?
Ans. Methane (CH₄) is used as fuel and this is the main ingredient of bio gas and compressed natural gas (C.N.G.).

Question 45.
What are ‘structural isomers’ ?
Answer:
Compounds with identical mole-cular formula but different structures are called structural isomers.

Question 46.
On what does the nature of the flame coming from the burning of hydrocarbon depends upon ?
Answer:
Saturated hydrocarbons will generally give a clean flame while unsaturated carbon compounds will give a yellow flame with lots of black smoke.

Question 47.
What presence makes soap uneffective in hard water?
Answer:
The presence of calcium and magnesium salts in hard water makes soap uneffective.

Short Answer Type Questions

Question 1.
How many structural isomers can be drawn for butane?
Answer;
Butane (C₄H₁₀) have two isomers –
1. n-butane (normal butane)

2. Iso-butane (normal butane)

Question 2.
Write the structural formula and functional group of Acetic acid and Ethyl Alcohol.
Answer:
1. Acetic acid –

2. Ethyl Alcohol –

Question 3.
Write the difference between soap and detergent.
Answer:
Difference between soap and detergent –

Soap	Detergent
1. Soaps are sodium or potassium salt of fatty acids (Carboxylic acids).	Detergents are ammonium or sulphonate salts of long chain carboxylic acid.
2. Soap does not form foam with hard water.	Detergents are also effective in hard water and forms foam.
3. Soap is prepared from vegetable oil or animal fat.	Synthetic detergents are formed by coal and hydrocarbons of petroleum.
4. Soap does not create water pollution.	Detergents creates water pollution.

Question 4.
How the carbon form a large number of compounds?
Or
Explain the versatile nature of Carbon.
Answer:
The versatile nature of carbon is due to the following reasons—
Tetravalency of Carbon:
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 elements. Compounds of carbon are formed with oxygen, hydrogen, nitrogen, sulphur, chlorine and many other elements giving rise to compounds with specific properties which depend on the elements other than carbon present in the molecule. .

The bonds that carbon forms with most other elements are very strong making these compounds exceptionally stable. Small size of Carbon: One 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.
Calination: Carbon has the unique ability to form bonds with other atoms of carbon, giving size to large molecules. This property is called catenation.

Question 5.
What is Alkyne? Write the general formula of this and write the name and electronic structure of simplest Alkyne also.
Answer:
Alkynes – Unsaturated carbon compounds formed by the combination of carbon and hydrogen, which have one triple bond is called Alkyne.
The general formula of Alkyne is C_nH_2n-2.
The first member of this series is Ethyne. The electronic structure of this is as under –

Question 6.
What is the importance of carbon? Explain.
Answer:
Carbon is very important in element and combined state both. Carbon is versatile element. Food, clothes, medicines, books, or many of the things are all based on carbon. In addition, all living structures are also based on carbon. The amount of carbon present in the earth’s crust and in the atmosphere is quite meagre. The earth’s crust has only 0.02% carbon in the form of minerals [like carbonates (CO₃^2-)] hydrogen – carbonates (HCO₃^–), coal and petroleum] and the atmosphere has 0.03% of carbon dioxide. In spite of this small amount of carbon available in nature, the importance of carbon seems to be immense.

Question 7.
Covalent bond is present in carbon compounds, not ionic, why? Explain it.
Answer:
The atomic number of carbon is 6 (2, 4). Its outer shell has four electrons. During bond formation atoms have tendency to attain noble gas configuration. Elements forming ionic compounds archieve this by either gaining or losing electrons from file outermost shell. 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 –

1. It could gain four electrons forming C^4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
2. 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 only- two electrons.
So the carbon compounds are not ionic and carbon forms covalent bond by sharing its valence electrons with other atoms of carbon or with atoms of other elements. Due to which both the atoms attains the noble gas configuration.

Question 8.
Explain the formation of coal and petroleum.
Answer:
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.

Question 9.
How the covalent bond is formed in H₂ and Cl₂ molecule? Explain.
Answer:
(1) H₂-The atomic number of hydrogen is one. Hence hydrogen has one electron in its K shell and it requires one more electron to fill the K shell. So two hydrogen atoms share their electrons to form a molecule of hydrogen (H₂). This allows each hydrogen atom to attain the electronic configuration of the nearest noble gas, helium and the shared pair of electrons forms a single bond between the two atoms of hydrogen.

(2) Cl₂ – Similar to H₂, Cl₂ also have single bond because the atomic number of chlorine atom is 17 (2, 8, 7) and becomes 8 electrons in the outermost shell of it by the sharing of one electron (configuration similar to Ar).

Question 10.
How the covalent bond is formed in O₂ and N₂? Explain.
Answer:
The atomic number of oxygen is eight so an atom of oxygen has six electrons in its L shell and it requires two more electrons to complete its octet. But the atomic number of nitrogen is seven so it requires three more electrons to complete its octet.

So each atom of oxygen shares two electrons with another atom of oxygen and each atom of nitrogen shares three electrons with another atom of nitrogen and forms double and triple bond successively and inert gas configuration is attained.

Question 11.
Why alkaline potassium permanganate and acidified potassium dichro-mate are known as ‘oxidising’ agents?
Answer:
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.

Question 12.
What are hetroatom ? Give example ?
Answer:
Carbon forms bonds with other elements such as halogens, oxygen, nitrogen and sulphur. In a hydrocarbon chain, one or more hydrogens can be replaced by these elements, such that the valency of carbon remains satisfied. In such compounds, the element replacing hydrogen is referred to as hetro atom.

Question 13.
How the inert gas conifguration of atoms is attained in CH₄, NH₃ and H₂O. represent it with electron dot structure.
Answer:
(1) Methane (CH₄)

(2) NH₃ (Ammonia)

H₂O (Water)

In the formation of these molecules C, N and O attains the configuration similar to Ne (2, 8) and H(2), similar to He.

Question 14.
What is functional group? Explain with examples.
Answer:
Functional group – Those hetero-atom or group of atoms which represents the specific properties to carbon compound is called functional group.
Some functional groups in carbon compounds are as under –

Free valency or valencies of the group are shown by single lines by which functional group is attached the carbon chain

Question 15.
Why it is stated in some adver-tisements that some vegetable oils are ‘healthy’ ?
Answer:
Generally, animal fats contain saturated fatty acids which are said to be harmful for health. Whereas vegetable oils generally have long unsaturated carbon chains therefore, they are called healthy.

Question 16.
In the homologous series, a gradation in physical properties is seen. Why?
Answer:
As the molecular mass increases in any homologous series, a gradation in physical properties is seen. This is because the melting and boiling points increase with increasing molecular mass.

Question 17.
Calculate the difference in formulae and molecular masses.
(a)
1. CH₃-OH and C₂H₅OH
2. C₂H₅OH and C₃H₇OH
3.  C₃H₇OH and C₄H₉OH
(b) Is any similarities in these three?
(c) To prepare a family, arrange these Alcohols in the increasing order of carbon atoms. Is this may the called a family of homologous series?
Answer:
(a) There is difference of CH₂ in these formulae so the difference in molecular mass is 14.
(b) All the three group belongs to same homologous series because same functional group (-OH) substitutes Hydrogen, present in the carbon chain.

These compounds belongs to same Homologous series (family) which is Alcohol series.

Question 18.
Define Alkane, Alkene and Alky- ne and write the general formula of these.
Answer:
1.  Alkane – The saturated carbon compounds (Hydrocarbons) formed by the combination of carbon and hydrogen, which have single bond between carbon atoms are called Alkanes. General formula of Alkanes is CO_nH_2n+2 where n = 1, 2, 3, 4,….

2. The unsaturated hydrocarbons formed by the combination of carbon and hydrogen which have double bond between, carbon atoms are called Alkenes.
General formula of Alkenes is C_nH_2n where n = 2, 3, 4 ….

3. The unsaturated hydrocarbons formed by the combination of carbon and hydrogen having triple bond between carbon atoms are called Alkynes.
General formula of Alkynes is C_nH_{2n- 2} where n = 2, 3, 4 ….

Question 19.
The coal or charcoal in an ‘angithi’ sometimes just glows red and gives out heat without a flame. Why ?
Answer:
This is because a flame is only produced when gaseous substances burn. When wood or charcoal is ignited, the volative substances present vapourise and bum with a flame in the beginning.

Question 20.
(a) Two Alkanes have 4 and 6 carbon atoms successively then what will be the physical state of these at room temperature?
(b) Write the formula and name of third and fifth member of Homologous series with general formula C_nH_{2n- 2} .
Answer:
(a) Alkane having four carbon atoms is butane, which is gas at room temperature but the Alkane having six carbon atoms is hexane which is liquid at room temperature.

(b) The general formula C_nH_{2n- 2} belongs to Alkyne series which starts from n = 2. So will be equal to four. For the third member of this series and n will be equal to six for fifth member. So the third member of this series is butyne (C₄H₆) and fifth member of this series is hexyne (C₆H₁₀).

Question 21.
A organic compound A having molecular formula C₂H₆O gives Carboxylic Acid B. On oxidation which have the number of carbon atoms equal to A. Compound A is used by doctors for sterili-sation of skin then what is the name of compound A and B and write the equation of the reaction for the formation B from A.
Answer:

So the B is organic acid having two carbon atoms with —COOH group. So B is CH₃OCOOH carboxylic acid is formed by the oxidation of alcohol and alcohol is used to sterilise the skin. So the compound A (C₂H₆O) is alcohol and equation of the chemical reaction for the formation of B.
From A is as under –

Question 22.
What is ‘denatured alcohol’ ?
Or
What do you understand by ‘denatu- ration’ of alcohol’ ?
Answer:
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 to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.

Question 23.
The boiling points of three saturated Hydrocarbon A, B and C are – 162°C, – 42.2°C and – 0.5°C. Successively then which hydrocarbon have maxi-mum number of carbon atoms?
Ans.
Compound C have maximum number of carbon atoms because the boiling point of it is maximum. Molecular mass increases with increase in number of carbon atoms so attraction force between molecules increases as a result melting point and boiling point also increases.

Question 24.
Write the two tests which represent the acidic property of acetic acid (CH₃COOH).
Answer:
These tests are performed to represent the acidic property of acetic acid.
(1) Litmus Test – When few drops of acetic acid are added on blue litmus then it becomes red which proves the acidic property of it.

(2) Sodium bicarbonate Test – When solution of sodium bicarbonate is added in acetic acid, CO ₂ gas is liberated with effervescence which again proves the acidic property of acetic acid.

Question 25.
A neutral organic compound A, having molecular formula C₂H₆O, gives acidic compound B on oxidation with potassium-dichromate and sulphuric acid. When B again reacts with A in presence of hot and concetrate H₂SO₄ then a compound with sweet smell is formed. Identify the A, B and C and write the equations of the reactions.
Ans.

B is a acidic compound, which forms sweet smelling compound C by the reaction with A. So, C should be an ester and A will be an alcohol. So,
A = C₂H₅OH (Ethanol)
B = CH₃COOH (Ethanoic acid)
C = CH₃COOC₂H₅ (Ethyl Ethanoate)
The reactions will be as follows –

Question 26.
(a) The compounds of following formula belongs to which homologous series?
(i) C₂H₅NH₂
(ii)
(b) What is the structural difference between molecules of Aldehyde and Ketone?
Ans.
(a) (i) This compound belongs to amino series which have functional group, – NH₂.
(ii) This compound belongs to ketone series.
(b) Molecule of aldehyde and ketone both have >C = O (Carbonyl) group. In case of aldehyde one valance of carbonyl group is satisfied by H and another one by alkyl group so the functional group of aldehyde is -CHO but in case of ketone both the valancies of >C = O group are satisfied by alkyl group.

Question 27.
(a) Ethanol is soluble in water or not?
(b) What happens when ethanol reacts with hot and concentrated H₂SO₄?
Answer:
(a) Ethanol is liquid at room temperature and this is soluble in water. Ethanol can be mixed in water in any proportion.
(b) When ethanol reacts with hot and concentrated H₂OSO₄, ethene is formed due to dehydration of it.

In this reaction the concentrated sulphu-ric acid act as dehydrating agent which removes water from ethanol.

Question 28.
What is ‘esterification’. Explain.
Answer:
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. This is called esterification.

Question 29.
What is ‘Saponification’ ? What is its use ?
Answer:
On treating ester with sodium hydroxide, which is an alkali, the ester is converted back to alcohol and sodium salt of carboxylic acid. This reaction is known as saponification.

This reaction is used in the preparation of soap. Soaps are sodium or potassium salts of long chain carboxylic acid.

Question 30.
How do Ethanol and Methanol affect living beings? Explain.
Answer:
Effect of Ethanol (C₂H₅OH) and Methanol (CH₃OH) on living beings— When large quantity of ethanol is 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, and finally stupour. Although a person feel relaxed but does not realise that his sense of judgement, sense of timing, and muscular coordination have been seriously impaired.

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. Methanol also affects the optic nerve, causing blindness.

Question 31.
Give the use of Alcohol as a fuel.
Answer:
Use of Alcohol as a fuel: Sugar-cane plants are the most efficient convertors of sunlight into chemical energy. Sugarcane juice is used to prepare molasses which isfermented to give alcohol (ethanol). Some countries use alcohol as an additive in petrol since it is a cleaner fuel wich gives rise to only carbon dioxide and water on burning in sufficient oxygen. ‘

Question 32.
Detergent can be used in hard water also. Why?
Answer:
Detergents are ammonium or sulphonate salts of long chain carboxylic acids. The charged ends of these compounds do not form unsoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water also. Detergents are generally used to make shampoos and products for cleaning clothes.

Essay Type Questions

Question 1.
Write the different Allotropes of carbon. Give the property, structure and uses of these Allotropes.
Answer:
The’ carbon occurs in different forms in nature with different physical properties. Due to the difference in the manner in which the carbon atoms are bonded to each other chemical properties of allotropes are same. Different allotropes of carbon are as follows –

1. Diamond: In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure. Diamond is the hardest substance known.

2. Graphite: In graphite, each carbon atoms is bonded to three other carbon atoms in the same plane giving a hexagonal structure. One of these bonds is a double bond and thus the valency of carbon is satisfied. Graphite structure is formed by the hexagonal structures being placed in layers one above the other.

The distance between carbon atoms of different layers is more due to hexagonal structure. So the possiblity of formation of covalent bonds between carbon atoms of opposite layers is negligible and fourth valance electron of carbon atoms remains almost free. So the flow of electrons in graphite is easy and it becomes good conductor of electricity. Graphite is smooth and slippery also.

3. Diamonds can be synthesised by subjecting pure carbon to very high pressure and temperature. These synthetic diamonds are small in size but are indistinguishable from natural diamonds.
4. Fullerenes form another class of allotropes of carbon. The first one to be identified was C-60 which has carbon atoms arranged in the shape of a football.

Question 2.
What is saturated hydrocarbon? Give the specific name for this series and write the structure of first six members of it.
Answer:
Saturated hydrocarbon – Carbon compounds formed by carbon and hydrogen which have single bond between carbon atoms are called saturated hydrocarbons.
Saturated hydrocarbons are known as Aikanes. The general formula of Aikanes is C_nH_2n+2 where n = 1, 2, 3, 4 …. The first six members of Alkane series are methane, ethane, propane, butane, pentane and hexane. ihe structure of these is as follows :

Question 3.
What is isomerism? Explain with example.
Answer:
Isomerism – Compounds with same molecular formula but different properties are called isomers of each other and this property is called isomerism.
Compounds with same molecular formula but different structures are called structural isomers. For example – if we make the carbon skeleton with four carbon atoms, then two different skeletons are possible.

Filling the remaining valencies with hydrogen the structures obtained are as follows –

Both these structures have the same molecular formula C₄H₁₀ which is butane. So this is the example of structural isomerism.

Question 4.
Explain the method of nomen-clature of carbon compounds in detail.
Answer:
The names of compounds in a homologous series are based on the name of the basic carbon chain modified by a ‘prefix’, ‘phrase before’ or ‘suffix’ ‘phrase after’ indicating the nature of the functional group.
Following names are given on the basis of number of carbon atoms
1C = Meth
2C = Eth
3C = Prop
4C = But
5C = Pet
6C = Hex etc.
Naming a carbon compound can be done by the following Rules –

(1) Identify the number of carbon atoms in the compound. A compound having three carbon atoms would have the name propane and when four carbon atoms are present then have the name butane.

(2) In case a functional group is present, it is indicated in the name of the compound with either a prefix or a suffix (as given in Table).

(3) If the name of the functional group is to be given as a suffix, and the suffix of the functional group begins with a vowel a, e, i, o, u then the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix. For example, a three-carbon chain with a ketone group would be named in the following manner—
Propane – ‘e’ = propan + ‘one’ = propanone.

(4) If the carbon chain is unsaturated, then the final ‘ane’ in the name of the carbon chain is substituted by ‘ene’ or ‘yne’. For example, a three-carbon chain with a double bond is called propene and if it has a triple bond then it is called propyne.

Question 5.
Give the property of Ethanoic add and explain the following reactions of it
(a) Esterification
(b) Reaction with Base
(c) Reaction with sodium carbonate and sodium bicarbonate.
Answer:
Properties of Ethanoic 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 is used 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. So this is known as glacial acetic acid.
Ethanoic acid is acidic in nature but unlike inorganic mineral acids like HCl, this is very weak acid.

Reactions of Ethanoic acid –
(a) Esterification reaction -Esters are mainly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with, alcohol in presence of an acid catalyst to give an ester and this reaction is called esterification.

(b) Reaction with a base—Ethanoic acid reacts with a base such as sodium hydroxide to give a salt (sodium ethanoate or sodium acetate) and water.
CH₃COOH + NaOH >CH₃COONa + H₂O

(c) Reaction with Sodium carbonate and Sodium hydrogen carbonate – Ethanoic acid reacts with Sodium carbonate and Sodium hydrogen carbonate to give rise a salt, carbondioxide and water. The salt produced in this reaction is called sodium acetate (sodium ethanoate).

Question 6.
Write the chemical properties of carbon compounds.
Answer:
The main chemical properties of carbon compounds are as follows –
1. Combustion: Carbon, in all its allotropic forms, burns in oxygen to give carbon dioxide along with the release of heat and light. For example –

Saturated hydrocarbons bums with a clean flame while unsaturated carbon compounds bums with yellow flame with black smoke.
2. Oxidation—Carbon compounds can
be easily oxidised on combustion. In addition to complete oxidation there are some reactions in which alcohols are converted to carboxylic acids.
Example –

3. Addition Reaction: In this reaction unsaturated hydrocarbons add hydrogen in presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst.

4. Substitution Reaction: Saturated hydrocarbons are fairly unreactive and inert in the presence of most reagents. However, in the presence of sunlight, chlorine reacts with hydrocarbons and the reaction is very fast. Chlorine replaces the hydrogen atoms one by one. It is called a substitution reaction because one type of atom or a group of atoms takes the place of another. A number of products are usually formed with the higher homologues of alkanes.

Question 7.
Write the properties of Ethanol. Explain the reactions of ethanol with –
(i) Sodium
(ii) Concentrated Sulphuric acid
(iii) Potassium permaganate
Answer:
Physical Properties of Ethanol –
The physical properties of ethanol are as under –

Ethanol is a liquid at room temperature. The melting point and boiling point of it are 156K and 35IK successively.
Ethanol is commonly called alochol and it is active ingredient of all alcoholic drinks.
It is a good solvent so it is used in medicines such as tincture iodine, cough syrups and tonics.
Ethanol is also soluble in water in all proportions.
Consumption of small quantities of dilute ethanol causes drunkenness.

Chemical properties of Ethanol –
(1) Reaction with Sodium: Ethanol reacts with sodium and forms sodium ethoxide with the evolution of hydrogen gas.

(2) Reaction with concentrated sulphuric acid – Heating ethanol at 443 K with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene –

In this reaction concentrated sulphuric acid act as a dehydrating agent which removes water from ethanol.
(3) Reaction with Potassium Permangnate – Potassium permangnate oxidise the ethanol into Ethanoic acid

Question 8.
(a) Write the dehydration reaction of ethanol and write the name of dehydrating agent.
(b) Choose correct series for the following –

Compounds	Series
(i) Ethane	(a) Unsaturated
(ii) Benzene	(b) Long chain saturated Hydrocarbon
(iii) Hexane	(c) Hydrocarbon
(iv) Methyl Alcohol	(d) Saturated Hydrocarbon carbon

Ans. (a) Equation of dehydration of ethanol –

Here sulphuric acid (H₂SO₄) act as dehydrating agent.
(b) (i) Ethane (d)
(ii) Benzene (a)
(iii) Hexane (b)
(iv) Methyl Alcohol (c)

Question 9.
(a) Write die formula of Benzene.
(b) Draw the structure of benzene and write the number of triple bonds present in it.
(c) Among the following, which is ethane? Write the number of bonds present in it.
(i) C₂H₂
(ii) C₂H₄
(iii) C₂H₆
Answer:
(a) Formula of benzene – C₆H₆
(b) Structure of benzene –

The number of triple bonds present in Benzene is zero.

The number of bonds present in ethane is 7.

Question 10.
(a) Write the formula of cyclohexane.
(b) Draw the structure of cyclohexane and write the number of bonds present in it.
(c) Which of the following in ethene ? Write the number of double bonds present in it.
(i) C₂H₂
(ii) C₂H₄
(iii) C₂H₆
Answer:
(a) Cyclohexane – C₆H₁₂
(b) Structure of Cyclohexane –

There are 18 single bonds present in cyclohexane.
(c) Ethene – C₂H₄

The number of double bonds present in ethene is one.

Question 11.
(a) Define alkanes, alkenes and alkynes.
(b) Write the general formula for each category.
(c) Write names of four members from each category and give their formula.
Answer:
(a) The compounds of hydrocarbon that are attached with only one bond between carbon atoms are called ‘alkanes’. Hydrocarbons that have one or more double bonds between carbon and carbon are called alkenes. Whereas hydrocarbons with one or more triple bonds between carbon- carbon are called alkynes.

(b) General formula –
Alkane = C_nH_2n+2
Alkene =
C_nH_2n
Alkyne =C_nH_2n-2 (n = 2, 3, 4)

(c) Members of alkane—
1. Ethane = C₂H₆
2. Propane = C₃H₈
3. Butane = C₄H₁₀
4. Pentane = C₅H₁₂

Members of alkene
1. Ethane = C₂H₄
2. Propene = C₃H₆
3. Butane = C₄H₈
4. Pentene = C₅H₁₀

Members of alkyne—
1. Ethyne = C₂H₂
2. Propyne = C₃H₄
3.Butyne = C₄H₆
4.Pentyne = C₅H₈

Question 12.
Give structural formula for the following carbon compounds and draw their electron dot structure.
(a) Methane and ethane
(b) Ethene and propene
(c) Ethyne and Propyne
Answer:
(a) Methane = CH₄
Structural formula –

Electron dot structure –

Ethane = C₂H₆
Structural formula –

Electron dot structure –

Ethene = C₃H₄
Structural formula –

Electron dot structure –

Propene = C₃H₆
Structural formula –

Electron dot structure –

(c) Ethyne = C₂H₂
Structural formula –
H – C ≡C – H
Electron dot structure –

Propyne = C₃H₄
Structural formula –

Electron dot structure –

Question 13.
Count the number of single, double and triple bonds in the following –
(a) Benzene
(b) Propanoic acid
(c) Propyne
(d) Ethanol
Answer:
(a) Benzene—C₆H₆

Single bonds = 9
Double bonds = 3
Triple bonds =0
(b) Propanoic acid—CH₃CH₂COOH

Single bonds = 9
Double bonds = 1
Triple bonds = 0
(c) Propyne—C₃H₄

Single bonds = 5
Double bonds = 0
Triple bonds = 1
(d) Ethanol—CH₃CH₂OH

Single bonds = 8
Double bonds = 0
Triple bonds = 0