Chapter 4 Carbon and Its Compounds

Text Book Part II

Question 1.
What would be the electron dot structure of carbon dioxide which has the formula CO₂?
Answer:
In carbon dioxide molecule, the two oxygen atoms are bonded on either side with carbon atom be double bonds. These there are 2 double bonds in CO₂. Carbon shares its electrons in the formation of a double bond with one
oxygen atom and another two electrons with another oxygen atom. In this process, both the oxygen atoms and the carbon atom acquire the stable electronic configuration of the noble gas neon. The formation of CO₂ molecule is shown below.

Question 2.
What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur?
(Hint – The eight atoms of sulphur are joined together in the form of a ring.)
Answer:

Text Book Part II Page No. 12

Question 1.
How many structural isomers can you draw for pentane?
Answer:
Pentane has 3 structural isomers. We can write as follows.
i) CH₃-CH₂-CH₂-CH₂-CH₃

Question 2.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Answer:

1.                  Catenation: It is the ability to form bonds with other atoms of carbon.

2.                  Tetravalency: With the valency of four, carbon is capable of bonding with four other atoms.

Question 3.
What will be the formula and electron dot structure of cyclopentane?
Answer:
Molecular formula of cyclopentane is: C₅H₁₀
Electron dot structure:

Question 4.
Draw the structures for the following compounds.

1.                  Ethanoic acid

2.                  Bromopentane*

3.                  Butanone

4.                  Hexanal.

* Are structural isomers possible for bromopentane ?
Answer:

Question 5.
How would you name the following compounds?
(i) CH₃—CH₂—Br


Answer:

1.                  Bromoethane

2.                  Methanol

3.                  Hexane.

Text Book Part II Page No. 15

Question 1.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer:
Addition reaction means adding oxygen. Adding ethanol to potassium permanganate, we get ethanoic acid. Hence this reaction is called oxidation reaction.

Question 2.
A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Answer:
Air, also contains other gases like nitrogen, carbon dioxide and few more gases apart from oxygen. When ethyne is burnt in air, it gives a sooty flame. This is due to incomplete combustion caused by the limited supply of oxygen. However, if ethyne is burnt with oxygen, it gives a clean flame with temperature 3000°C because of complete combustion. This oxy-acetylene flame is used for welding. It is not possible to attain such a high temperature without mixing oxygen. This is the reason why a mixture of ethyne and air is not used,
2HC ≡ CH + 5O₂ → 4CO₂ + 2H₂O + Heat.

Text Book Part II Page No. 18

Question 1.
How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer:
All the carboxylic acids decompose sodium hydrogen carbonate giving brisk effervescence of carbon dioxide gas whereas ethanol does not react with sodium hydrogen carbonate

Experiment:

1.                  Take two test tubes, label them as A and B

2.                  Take about 0.5 g of sodium hydrogen carbonate (NaHco₃) in each test tube

3.                  Add 2 ml of ethanol in test tube A and 2ml of ethanoic acid in test tube B.

4.                  We can observe the gas bubbles in test tube B. No such bubbles are seen in test tube A. Pass the gas produced in test tube B through lime water taken in another test tube

5.                  We will find that lime water turns milky It is a test for carbon dioxide.

Hence, this experiment proves that when ethanoic acid reacts with sodium hydrogen carbonate, then carbon dioxide gas is produced with an effervescence (a rapid evolution of gas bubbles). Ethanol does not react with NaHCO₃.

Question 2.
What are oxidising agents?
Answer:
Oxidising agents are the substances that gain electrons in redox reaction and whose oxidation number is reduced. Examples: KMnO₄ or K₂Cr₂O₇. They have the ability to oxidize or give their oxygen to other substances.

Text Book Part II Page No. 20

Question 1.
Would you be able to check if water is hard by using a detergent?
Answer:
Detergent gives lather both with hard and soft water, while a soap gives lather with soft water only. Thus, it is not possible to check if the water is hard by using a detergent.

Question 2.
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
Answer:
A soap molecule has two parts namely hydrophobic and hydrophilic. With the help of these particles, it attaches to the grease or dirt particle and forms a cluster called micelle. These micelles remain suspended as a colloid. To remove these micelles, it is necessary to agitate clothes.

KSEEB SSLC Class 10 Science Chapter 4 Textbook Exercises

Question 1.
Ethane, with the molecular formula C₂H₆ has
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.
Answer:
(b) 7 covalent bonds.

Question 2.
Butanone is a four-carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone.
(d) alcohol.
Answer:
(c) ketone.

Question 3.
While cooking, if the bottom of the vessel is getting blackened on the outside, it means that
(a) the food is not cooked completely.
(b) the fuel is not burning completely.
(c) the fuel is wet.
(d) the fuel is burning completely.
Answer:
(b) the fuel is not burning completely.

Question 4.
Explain the nature of the covalent bond using the bond formation in CH3Cl.
Answer:
Carbon has a valency of four. It shares one electron to each 3 hydrogen atoms and one more electron with chlorine.

Question 5.
Draw the electron dot structures for
(a) ethanoic acid.
(b) H₂S.
(c) propanone.
(d) F₂.
Answer:
a) Ethanoic acid

b) H₂S

c) propanone

(d) F₂

Question 6.
What is an homologous series? Explain with an example.
Answer:

A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group. Every next member of a homologous series has a clear difference of 14 units of mass.

For example, methane, ethane, propane, etc., are all part of the alkane homologous series. The general formula of this series is C_nH_2n+2.

An example is explained with formula as below:

1.                  Methane, CH₄

2.                  Ethane, CH₃CH₃

3.                  Propane, CH₃CH₂CH₃

4.                  Butane, CH₃CH₂CH₂CH₃

It can be noticed that there is a difference of -CH₂ unit between each successive compound.

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Answer:

Ethanol and Ethanoic acid can be differentiated on the basis of their following properties by:

1.                  Ethanol is a liquid at room temperature with a pleasant smell. Ethanoic acid has a melting point of 17°C. Since it is below the room temperature so, it freezes during winter. Moreover, ethanoic acid has a smell like vinegar.

2.                  Ethanol does not react with metal carbonates while, ethanoic acid reacts with metal carbonates to form a salt, water and carbon dioxide.
For example:
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ +H₂O

3.                  Ethanol does not react with NaOH while ethanoic acid reacts with NaOH to form sodium ethanoate and water.
For example,
CH₃COOH + NaOH → CH₃COONa + H₂O

4.                  Ethanol is oxidized to give ethanoic acid in the presence of acidified KMnO₄ while no reaction takes place with ethanoic acid in the presence of acidified KMnO₄.

Difference in physical properties:

Ethanol	Ethanoic acid
This is in liquid form at room temperature. Its melting point is 156° K.	Its melting point is 290K and hence it often freezes during winter in cold climates.
Difference in chemical properties
Ethanol will not react with metallic carbo­nates.	Ethanoic acid reacts with carbo­nates and Hydrogen carbonate and forms salts, carbon dioxide and water.

Question 8.
Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Answer:
A soap molecule has two ends. One end is hydrophilic and another end is hydrophobic. When soap is dissolved in water and clothes are put in the soapy solution, soap molecules converge in a typical manner to make a structure is called micelle. The hydrophobic ends of different molecules surround a particle of grease and make the micelle, which is a spherical structure.

In this, the hydrophilic end is outside the sphere and hydrophobic end is towards the centre of the sphere. This is why micelle formation takes place when soap is added to water. Since ethanol is not as polar as soap, micelles will not be formed in other solvents such as ethanol.

Question 9.
Why are carbon and its compounds used as fuels for most applications?
Answer:
Carbon in all its allotropic forms, burns in oxygen to give carbondioxide along with the release of heat and light. Most carbon compounds also release a large amount of heat and light on burning. Hence carbon and its compounds are used as fuels for most applications.

Question 10.
Explain the formation of scum when hard water is treated with soap.
Answer:
Hard water often contains salts of calcium and magnesium. Soap molecules react with the salts of calcium and magnesium and form a precipitate. This precipitate begins floating as an off-white layer over water. This layer is called scum. Soaps lose their cleansing property in hard water because of the formation of scum.

Question 11.
What change will you observe if you test soap with litmus paper (red and blue)?
Answer:
Soap is basic in nature, hence red litmus changes to blue. Blue litmus is seen blue only.

Question 12.
What is hydrogenation? What is its industrial application?
Answer:

Hydrogenation is a reaction between hydrogen and other compounds in the presence of the desired catalyst. Hydrogenation is used for reducing saturated hydrocarbons. Hydrogenation is an addition reaction. For example: When ethane is heated with the catalyst, nickel, it is reduced to ethane.

Industrial application:

1.                  In the petrochemical industry, hydrogenation is used to convert alkenes into alkanes (paraffin) and cyclo-alkanes.

2.                  It is also used to prepare vegetable cooking fat from vegetable oils.

Question 13.
Which of the following hydro-carbons undergo addition reactions:
C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄.
Answer:
C₂H₆ and C₂H₂ are unsaturated Hydrocarbons. Hence these undergo addition reactions.

Question 14.
Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.
Answer:
Butter contains saturated fats. Therefore, it cannot be hydrogenated. On the other hand, oil has unsaturated fats. That is why it can be hydrogenated to saturated fats (solids).

Question 15.
Explain the mechanism of the cleaning action of soaps.
Answer:

Soap are molecules in which the two ends have differing properties. One is hydrophilic, that is, it interacts with water, while the other end is hydrophobic, that is, it interacts with hydrocarbons. In the clusters of molecules in which the hydrophobic tails are on the surface of the cluster. This formation is called micelle.

Since the oily dirt will be collected in the centre of the micelle. 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 rinsed away.

KSEEB SSLC Class 10 Science Chapter 4 Additional Questions and Answers

Question 1.
Write the electron dot formula of O₂.
Answer:

Question 2.
What is substitution Reaction? Give an example.
Answer:
If one type of atom or a group of atoms takes the place of another, it is called substitution reaction.
Eg: CH₄ + Cl₂ CH₃Cl + HCl (in the presence of sunlight)

Question 3.
Name 2 commercially important compounds.
Answer:
Ethanol and ethanoic acid.

Question 4.
Give an example for Esterification reaction.
Answer:

Question 5.
Write one use of ester.
Answer:
Esters are used in making perfumes and as flourishing agents.

Question 6.
What are detergents?
Answer:
Detergents are generally sodium salts of sulphonic acids or ammonium salts with chlorides or bromides etc.

Question 7.
Where is Ethanol used?
Answer:
It is used in medicines such as tincture iodine, cough syrups, and many tonics.

Question 8.
What is vinegar? Mention one of its use.
Answer:
5 to 8% solution of acetic acid in water is called vinegar. It is used as a preservative in pickles. We hope the given KSEEB SSLC Class 10 Science Solutions Chapter 4 Carbon and Its Compounds will help you. If you have any query regarding Karnataka SSLC Class 10 Science Solutions Chapter 4 Carbon and Its Compounds, drop a comment below and we will get back to you at the earliest.

Access Answers to NCERT Class 10 Science Chapter 4 – Carbon and Its Compounds

(All In-text and Exercise Questions Solved)

In-text questions set 1, page number 61

1. What would be the electron dot structure of carbon dioxide which has the formula CO₂?

Solution:

2. What would be the electron dot structure of a molecule of Sulphur which is made up of eight atoms of Sulphur? (Hint – The eight atoms of Sulphur are joined together in the form of a ring).

Solution:

In-text questions set 2, page number 61

1. How many structural isomers can you draw for pentane?

Solution: The structural isomers of pentane are as follows:

n-pentane

2-methylbutane

2, 2-dimethylpropane

 

2-methylbutane

 

2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

Solution: Two properties of carbon which lead to the huge number of carbon compounds we see around us are as given below:

• Carbon has six valence electrons which is actually a high number of valency.
• Covalent bonding happens easily with carbon atoms and numerous others, such as oxygen, chlorine, nitrogen, sulphur, hydrogen, etc.

3. What will be the formula and electron dot structure of cyclopentane?

Solution: The formula and electron dot structure of cyclopentane is as given below:

4. Draw the structures for the following compounds.

(i) Ethanoic acid

(ii) Bromopentane*

(iii) Butanone

(iv) Hexanal

Solution: i)

 

ii)

iii)

iv)

5. How would you name the following compounds?

• CH₃—CH₂—Br
• 
• 

Solution:

•  

1.                  Bromoethane

2.                  Methanal or Formaldehyde

3.                  1 – Hexyne

In-text questions set 3, page number 71

1. How is the conversion of ethanol to ethanoic acid an oxidation reaction?

Solution:

The conversion of ethanol to ethanoic acid involves the removal of the hydrogen atom and the addition of oxygen, and it is an oxidation reaction. In the first step, a H₂ molecule is removed from ethanol to form ethanal. As the loss of hydrogen is oxidation, so the reaction is an oxidation reaction. Similarly, an oxygen atom is added to form ethanoic acid from ethanal. As the gain of oxygen is called oxidation, the reaction is an oxidation reaction.

2. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

Solution: A mixture of oxygen and ethyne is burnt for welding instead of a mixture of ethyne and air because the production of heat is very important for welding metals. When oxygen and ethyne are burnt, it burns completely and produces a higher temperature than air and ethyne. Oxygen and ethyne produce a very hot blue flame, but the mixture of air and ethyne gives out a sooty flame which means that there are unburnt particles, resulting in lesser heat.

In-text questions set 4, page number 74

1. How would you distinguish experimentally between an alcohol and a carboxylic acid?

Solution: In reaction with sodium carbonate, carboxylic acids produce carbon dioxide gas which turns lime water milky, whereas alcohols do not give this reaction. This experiment can be used to distinguish alcohol and carboxylic acid.

The reaction of the carboxylic acid with sodium carbonate:

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂

2. What are oxidising agents?

Solution: Oxidising agents are those compounds which either remove hydrogen or add oxygen to a compound. For example, halogens, potassium nitrate, and nitric acid.

In-text questions set 5, page number 76

1. Would you be able to check if water is hard by using a detergent?

Solution: It is not possible to check if water is hard by using a detergent because detergents are salts of ammonium or sulphonates of long-chain carboxylic acids. Unlike soaps, they do not react with calcium and magnesium to distinguish the nature of water.

2. People use a variety of methods to wash clothes. Usually, after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?

Solution: Agitation is necessary to get clean clothes as it aids soap micelles to trap the oil, grease or any other impurities that have to be removed. When they are being beaten or agitated, the particles are removed from the clothes’ surfaces and go into the water, thus cleaning the clothes.

Exercise questions, page number 77-78

1. Ethane, with the molecular formula C₂H_6, has

(a) 6 covalent bonds

(b) 7 covalent bonds

(c) 8 covalent bonds

(d) 9 covalent bonds

Answer: (b) 7 covalent bonds

Solution: Ethane, with the molecular formula C₂H_6, has 7 covalent bonds.

2. Butanone is a four-carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol

Answer: (c) ketone

3. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

(a) the food is not cooked completely

(b) the fuel is not burning completely

(c) the fuel is wet

(d) the fuel is burning completely

Answer: (b) the fuel is not burning completely

Solution: While cooking, if the bottom of the vessel is getting blackened on the outside indicates that the fuel is not burning completely.

4. Explain the nature of the covalent bond using the bond formation in CH₃Cl.

Solution: Carbon can neither lose 4 electrons nor gain four electrons as these processes make the system unstable due to the requirement of extra energy. Therefore, CH₃Cl completes its octet configuration by sharing its 4 electrons with carbon atoms or with atoms of other elements. Hence, the bonding that exists in CH₃Cl is a covalent bonding.

Here, carbon requires 4 electrons to complete its octet, while each hydrogen atom requires one electron to complete its duplet. Also, chlorine requires an electron to complete the octet. Therefore, all of these share electrons, and as a result, carbon forms 3 bonds with hydrogen and one with chlorine.

5. Draw the electron dot structures for

(a) ethanoic acid

(b) H₂ S

(c) propanone

(d) F₂

 

Solution:

a)

b)

c)

d)

6. What is a homologous series? Explain with an example.

A homologous series is a series of compounds which has the same functional group. This also contains a similar general formula and chemical properties. Since there is a change in the physical properties, we can say that there would be an increase in molecular size and mass.

For example, methane, ethane, propane, butane, etc., are all part of the alkane homologous series. The general formula of this series is C_nH_2n+2. Methane CH₄ Ethane CH₃CH₃ Propane CH₃CH₂CH₃ Butane CH₃CH₂CH₂CH₃. It can be noticed that there is a difference of −CH2 unit between each successive compound.

7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

Solution:

Ethanol	Ethanoic acid
It does not react with sodium hydrogen carbonate	Bubbles and fizzes with sodium hydrogen carbonate
A good smell	Smells like vinegar
No action in litmus paper	Blue litmus paper to red
Burning taste	Sour taste

8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents, such as ethanol also?

Solution: Micelle formation takes place because of the dirt particles in water and clean water. There are two mediums that are involved: one is pure water, and the other is dirt, also called impurities. The soap also has two mediums:

(i) organic tail

(ii) ionic head

So the organic tail mixes and dissolves with the dirt, whereas the oil or grease and ionic head dissolve and mix with the water. Therefore, when the material to be cleaned is removed from the water, the dirt is taken off by the soap molecules in the water. Hence, the soap cleans by forming closed structures through the mutual repulsion of the micelles (positively charged heads).

Other solvents, such as ethanol, in which sodium salt of fatty acids does not dissolve, so not able to form such micelles.

9. Why are carbon and its compounds used as fuels for most applications?

Solution: Carbon and its compounds are used as fuels for most applications because they have high calorific values and give out a lot of energy. Most of carbon compounds give a lot of heat and light when burnt in the air.

 10. Explain the formation of scum when hard water is treated with soap.

Solution: Scum is produced from the reaction of hard water with soap. Calcium and magnesium present in the hard water form an insoluble precipitate called scum.

11. What change will you observe if you test soap with litmus paper (red and blue)?

Solution: When soap is dissolved in water due to the formation of alkaline NaOH or KOH, the solution is alkaline. The solution changes the colour of the red litmus to blue, but in the soap solution, the blue litmus remains blue.

12. What is hydrogenation? What is its industrial application?

Solution: Hydrogenation is a process or a chemical reaction between hydrogen and other compounds. It is usually done in the presence of catalysts. For example, nickel, palladium or platinum. Hydrogenation is used mainly to saturate organic compounds.

13. Which of the following hydrocarbons undergo addition reactions: C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH_4?

Solution: Unsaturated hydrocarbons undergo addition reactions. C₃H₆ and C₂H₂ are unsaturated hydrocarbons which undergo addition reactions.

14. Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.

Solution: The bromine water test is used to differentiate between the unsaturated compounds (like alkenes and alkynes) and the saturated compounds. For this purpose, bromine is used in the form of bromine water. A solution of bromine in water is called bromine water. Bromine water has a red-brown colour due to the presence of bromine in it. When bromine water is added to an unsaturated compound, then bromine gets added to the unsaturated compound, and the red-brown colour of bromine water is discharged. So, if an organic compound decolourises bromine water, then it will be an unsaturated hydrocarbon (containing a double bond or a triple bond), but saturated hydrocarbons (alkanes) do not decolourise bromine water.

The bromine water test is performed to differentiate between the unsaturated compounds (like alkenes and alkynes) and the saturated compounds. When bromine water is added to an unsaturated hydrocarbon, the red-brown colour of the bromine solution is discharged. So, if there is dis-colouration, then the compound will be an unsaturated hydrocarbon.

15. Explain the mechanism of the cleaning action of soaps.

Solution: There are so many impurities and dirt mixed in water, and most of all, the dirt does not dissolve in the water. Soap molecules are a combination of salts such as sodium or potassium. The molecules are of a long chain of carboxylic acids. So, when the carbon chain is dissolved in oil, and the ionic end is dissolved in the water, the soap starts cleansing and trapping the dirt. When this happens, the soap molecules form structures called micelles that are used for capturing the oil droplets, and then the other end is the ionic faces. This will then form an emulsion in water and help in dissolving the dirt or impurities when the clothes are washed.

The soap molecules have different properties at different ends. The first end is the hydrophilic end, which dissolves in the water and is attracted towards the water, and the second one is the hydrophobic end, which is dissolved in the hydrocarbons and is repulsive to water. The hydrophobic tail aligns itself along the surface of the water because it is not soluble in the water.

NCERT Solutions for Class 10 Science Chapter 4 – Carbon and Its Compounds

The average number of questions usually asked from this chapter is 2+3 marks. In the year 2017, a total of 15 mark questions were asked from this chapter, whereas in the year 2018, the weightage was 2+3 = 5.

List of Section Questions with Type

Section Number	Section Name	Questions	Question Type
Section 4.1	Bonding in carbon – The covalent bond	2	2 short answers
Section 4.2	Versatile nature of carbon	5	2 very short answers, 3 long answers
Section 4.3	Chemical properties of carbon compounds	2	2 long answers
Section 4.4	Some important carbon compounds – ethanol and ethanoic acid	2	1 short answer, 1 long answer
Section 4.5	Soaps and detergents	2	1 very short answer, 1 long answer

List of Exercise Questions with Type

This chapter consists of 15 questions and is divided into the following types –

Multiple-choice questions (MCQ)	3
Short answer (SA)	2
Long answer (LA)	7
Very long answer (VLA)	3

NCERT Solutions for Class 10 Science Chapter 4 – Carbon and Its Compounds

Carbon is the basis for all living organisms and a versatile element. It is tetravalent and has the property of catenation. Carbon forms covalent bonds by sharing electrons between two atoms and achieves completely filled outermost shell. It forms covalent bonds with oxygen, chlorine, hydrogen, nitrogen, sulphur and itself. It can form double and triple-bond compounds. There exist three types of carbon chains viz, branched, ring and straight. Carbon is considered as a major source of fuel. Ethanoic acid and ethanol are carbon compounds which are important and used in our daily lives. The behaviour of detergents and soaps is because of the hydrophilic and hydrophobic groups, which help in the emulsification of oily dirt and remove it.

Key Features of NCERT Solutions for Class 10 Science Chapter 4 – Carbon and Its Compounds

• The information given in these NCERT Solutions for Class 10 Science Chapter 4 – Carbon and Its Compounds is authentic and simple.
• These solutions provide answers to all the exercise questions at the end of Chapter 4, Carbon and Its Compounds, from NCERT Class 10 Science textbook.
• The solutions to questions printed between the lesson have also been provided.
• NCERT Solutions for Class 10 Science Chapter 4 – Carbon and Its Compounds are provided by expert teachers after expansive research.
• These solutions will be useful to prepare for the CBSE exam as well as various competitive exams.
• Students can refer to these solutions to prepare for their CBSE Board exam as it consists of step-by-step procedures, neatly labelled diagrams, shortcuts, and tips to tackle complex type of questions smartly.

Frequently Asked Questions on NCERT Solutions for Class 10 Science Chapter 4

Q1

What types of questions are present in Chapter 4 of NCERT Solutions for Class 10 Science?

The type of questions present in Chapter 4 of NCERT Solutions for Class 10 Science is as given below:
1. Multiple-choice questions – 3 questions
2. Short answer – 2 questions
3. Long answer – 7 questions
4. Very long answer – 3 questions

Q2

List out the topics in Chapter 4 of NCERT Solutions for Class 10 Science.

The topics in Chapter 4 of NCERT Solutions for Class 10 Science include the following:
1. Bonding in carbon – The covalent bond
2. Versatile nature of carbon
3. Chemical properties of carbon compounds
4. Some important carbon compounds – ethanol and ethanoic acid
5. Soaps and detergents

Q3

Where can I get the NCERT Solutions for Class 10 Science Chapter 4 online?

Class 10 is an important stage in every student’s life. The marks obtained in Class 10 will decide the career path of students. Hence, to achieve good results, the faculty at BYJU’S have created these solutions for all the chapters based on the CBSE syllabus. Students can download the NCERT Solutions available in PDF format from BYJU’S. The solutions are framed by keeping in mind the CBSE Board exam preparation of students irrespective of their intelligence quotient.

Important Questions with Answers

Multiple Choice Type Questions

Q1. C₃H₈ belongs to the homologous series of

(a ) Alkynes

(b ) Alkenes

(c ) Alkanes

(d ) Cycloalkanes

Answer:

(c ), C₃H₈ belongs to the homologous series of alkanes.

Q2. Which of the following will undergo an addition reaction?

(a ) CH₄

(b ) C₃H₈

(c ) C₂H₆

(d ) C₂H₄

Answer:

(d ) C₂H₄ is an alkene. Hence it will undergo an addition reaction.

Q3. In a diamond, each carbon atom is bonded to four other carbon atoms to form

(a ) A hexagonal array

(b ) A rigid three-dimensional structure

(c ) A structure in the shape of a football

(d ) A structure of a ring

Answer:

(b ), In a diamond, each carbon atom is bonded to four other carbon atoms to form a rigid three-dimensional structure.

Q4. The allotrope of carbon which is a good conductor of heat and electricity is

(a ) Diamond

(b ) Graphite

(c ) Charcoal

(d ) None of these

Answer:

(b ) The allotrope of carbon which is a good conductor of heat and electricity is graphite.

Q5. How many double bonds are there in a saturated hydrocarbon?

(a ) One

(b ) Two

(c ) Three

(d ) Zero

Answer:

(d ) A saturated hydrocarbon has zero double bonds.

Short Answer Type Questions

Q1. Draw the structural formula of ethyne.

Answer:

Structural Formula: H – C ≡ C – H

Q2. Write the names of the following compounds.

Answer:

(a ) Pentan-1-oic Acid

(b ) But-1-yne

(c ) Heptan-1-al

(d ) Pentan-1-ol

Q3. Identify and name the functional groups present in the following compounds.

Answer:

(a ) Propan-1-ol

(b ) Propan-1-oic Acid

(c ) Pent-3-one

(d ) But-1-ene

Q4. A compound X is formed by the reaction of carboxylic acid C₂H₄O₂ and alcohol in the presence of a few drops of H₂SO₄. The alcohol on oxidation with alkaline KMnO₄ followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of (a) carboxylic acid, (b) alcohol and (c) compound X. Also, write the reaction.

Answer:

Here, the carboxylic acid is ethanoic acid, alcohol is ethanol, and compound X is ethyl ethanoate.

Structure of Ethanoic Acid:

Structure of Ethanol:

Structure of Ethyl Ethanoate:

Reactions Involved:

CH₃COOH + CH₃CH₂COOH → CH₃COOC₂H₅ + H₂O

C₂H₅OH + Alkaline KMnO₄ → CH₃COOH

Q5. Why are detergents better cleansing agents than soaps? Explain.

Answer:

Detergents are better cleansing agents than soaps because we can use them even with hard water. Detergents have a more decisive cleansing action than soaps and are more soluble in water than soaps. The charged ends of detergents do not form insoluble precipitates with calcium and magnesium ions in hard water. When soap is used for washing clothes with hard water, it reacts with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum. Scum sticks to the cloth to be washed, making cleaning clothes difficult.

Q6. Name the functional groups present in the following compounds

(a ) CH₃COCH₂CH₂CH₂CH₃

(b ) CH₃CH₂CH₂COOH

(c ) CH₃CH₂CH₂CH₂CHO

(d ) CH₃CH₂OH

Answer:

(a ) A ketone functional group is present in the compound CH₃COCH₂CH₂CH₂CH_3.

(b ) A carboxylic acid functional group is present in the compound CH₃CH₂CH₂COOH.

(c ) An aldehyde functional group is present in the compound CH₃CH₂CH₂CH₂CHO.

(d ) An alcohol functional group is present in the compound CH₃CH₂OH.

Q7. How is ethene prepared from ethanol? Give the reaction involved in it.

Answer:

Ethanol is heated at 443 k in excess of concentrated sulphuric acid to obtain ethene.

CH₃​CH₂​OH + Conc. H₂​SO​₄ → CH₂ ​= CH₂​ + H₂​O

Q8. Intake of a small quantity of methanol can be lethal. Comment.

Answer:

Intake of a small quantity of Methanol can be lethal as it reacts rapidly with the components of cells. It causes the protoplasm to coagulate. It also affects the optic nerve and causes blindness.

Q9. Gas is evolved when ethanol reacts with sodium. Name the gas evolved and write the balanced chemical equation of the reaction involved.

Answer:

Hydrogen gas is evolved when ethanol reacts with sodium.

2 Na + 2 CH₃​CH₂​OH → 2 CH₃CH₂ONa + H₂

Q10. Ethene is formed when ethanol at 443 K is heated with excess concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced chemical equation of this reaction.

Answer:

Concentrated sulphuric acid removes water from ethanol, thereby acting as a dehydrating agent.

CH₃​CH₂​OH + Conc H₂SO₄ → CH₂ = CH₂ + H₂O

Q11. Carbon, the Group (14) element in the Periodic Table, is known to form compounds with many elements. Write an example of a compound formed with

(a ) Chlorine (Group 17 of the periodic table)

(b ) Oxygen (Group 16 of the periodic table)

Answer:

(a ) Carbon tetrachloride (CCl₄)

(b ) Carbon dioxide (CO₂)

Q12. Crosses or dots in the electron dot structure represent the valence shell electrons.

(a) The atomic number of chlorine is 17. Write its electronic configuration

Answer:

(a ) The electronic configuration of chlorine atom is 2, 8, 7

Q13. Catenation is the ability of an atom to form bonds with other atoms of the same element. Both carbon and silicon exhibit it. Compare the ability of catenation of the two elements. Give reasons.

Answer:

Both carbon and silicon show catenation. But compounds made with silicon are more reactive and less stable. In contrast, bonds formed by carbon are very strong, so organic compounds are more stable than silicon compounds. Thus, we can say that carbon shows better catenation than silicon.

Q14. Unsaturated hydrocarbons contain multiple bonds between the two C-atoms and show addition reactions. Give the test to distinguish ethane from ethene.

Answer:

The bromine water test can be used to distinguish between saturated and unsaturated hydrocarbons. Saturated compounds don’t give an addition reaction. Hence, there won’t be any change in the reaction mixture. In contrast, if an unsaturated hydrocarbon is added to bromine water, its colour will decolourise.

Saturated hydrocarbon + Br₂ → No Reaction (No Colour Change)

Unsaturated hydrocarbon + Br₂ → Reaction will occur (Decolourise)

Q15. Match the reactions given in Column (A) with the names given in column (B).

Column (A)	Column (B)
CH3OH + CH3COOH + H+ → CH3COOCH3 + H2O	Addition reaction
CH2 = CH2 + H2 + Ni → H3C – CH3	Substitution reaction
CH4 + Cl2 + Sunlight → CH3Cl + HCl	Neutralisation reaction
CH3COOH + NaOH → CH3COONa + H2O	Esterification reaction

Answer:

Column (A)	Column (B)
CH3OH + CH3COOH + H+ → CH3COOCH3 + H2O	Esterification reaction
CH2 = CH2 + H2 + Ni → H3C – CH3	Addition reaction
CH4 + Cl2 + Sunlight → CH3Cl + HCl	Substitution reaction
CH3COOH + NaOH → CH3COONa + H2O	Neutralisation reaction

Q16. Write the structural formulae of all the isomers of hexane.

Answer:

There are five isomers of hexane.

Q17. What is the role of metal or reagents written on arrows in the given chemical reactions?

 

Answer:

(a ) Ni acts as a catalyst.

(b ) Concentrated H₂SO₄ acts as a catalyst and a dehydrating agent.

(c ) Alkaline KMnO₄ acts as an oxidising agent.

Long Answer Type Questions

Q1. A salt X is formed, and gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one you have named. Also, write a chemical equation of the reaction involved.

Answer:

The salt X is sodium ethanoate (CH₃​COONa), and the evolved gas is carbon dioxide (CO₂​).

Take a test tube and add ethanoic acid (CH₃​COOH). Add sodium bicarbonate (NaHCO₃​) to the acid, close the test tube’s mouth with a cork, and attach a delivery tube.

Take lime water in another test tube and attach it to the delivery tube. The lime water turns milky. This indicates that the evolved gas is carbon dioxide.

Ca(OH)_2​ + CO_2​ ​→ CaCO₃ ​+ H_2​​O

The milkiness is due to the formation of CaCO₃.

Reaction Involved: CH₃COOH + NaHCO₃ ​→ CH₃COONa + H₂​O + CO₂ (g)

Q2. (a ) What are hydrocarbons? Give examples.

(b ) Give the structural differences between saturated and unsaturated hydrocarbons with two examples each.

(c ) What is a functional group? Give examples of four different functional groups.

Answer:

(a ) A hydrocarbon is any of a class of organic compounds made up of carbon and hydrogen. Methane and Ethane are examples of hydrocarbons.

(b )

S. No.	Saturated hydrocarbon	Unsaturated hydrocarbon
1.	Saturated hydrocarbons contain carbon-carbon single bonds.	Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond.
2.	They have sp3 hybridised carbon atoms having a general formula CnH2n + 2.	They have sp2 or sp hybridised carbon atoms having a general formula CnH2n or CnH2n – 2.

(c ) A functional group is the atoms group in a molecule that specifies the chemical behaviour of the molecule. Atoms in a functional group are bonded by the covalent bond.

Q3. Name the reaction which is commonly used in the conversion of vegetable oils to fats. Explain the reaction involved in detail.

Answer:

Vegetable oils generally have long chains of unsaturated carbons, while animal fats have long chains of saturated carbons. An addition reaction is used in the conversion of vegetable oils to fats. It is known as the hydrogenation of oil.

An addition reaction is carried out in the presence of Ni as a catalyst.

Q4. (a ) Write the formula and draw the electron dot structure of carbon tetrachloride.

(b ) What is saponification? Write the reaction involved in this process.

Answer:

(a ) The formula of carbon tetrachloride is CC₄.

Electron dot structure of Carbon tetrachloride:

(b ) Saponification is a methodology of manufacturing soap by the hydrolysis of fats or oils with a base like sodium hydroxide.

Reaction: CH₃​COOC₂​H₅ + NaOH → CH₃​COONa + C₂​H₅​OH

Q5. Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and reaction in preparing an ester with a well-labelled diagram.

Answer:

Esters are produced by heating carboxylic acids with alcohols in the presence of an acid catalyst. The catalyst that can be used is concentrated sulphuric acid.

CH₃COOH + CH₃CH₂OH + Conc. H₂SO₄ ⟶ CH₃CH₂COOCH₂CH₃ + H₂O

Q6. A compound C (molecular formula, C₂H₄O₂) reacts with Na – metal to form a compound R and evolves into a gas which burns with a pop sound. Compound C on treatment with an alcohol A in the presence of an acid forms a sweet-smelling compound S (molecular formula, C₃H₆O₂). On addition of NaOH to C, it also gives R and water. S on treatment with NaOH solution gives back R and A. Identify C, R, A, and S and write down the reactions involved.

Answer:

Here, compound C is ethanoic acid (CH₃COOH), compound R is sodium ethanoate (CH₃COONa), compound A is ethanol (C₂H₅OH), and compound S is ethyl ethanoate (CH₃COOC₂H₅).

• Ethanoic acid (CH3COOH) reacts with sodium metal to form sodium ethanoate (CH₃COONa).

2 CH₃COOH + 2 Na → 2 CH₃COONa + H₂

• Ethanoic acid (CH₃COOH) on treatment with ethanol (C₂H₅OH) in the presence of an acid forms a sweet-smelling ethyl ethanoate (CH₃COOC₂H₅).

CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O

• On adding NaOH to ethanoic acid (CH₃COOH), it also gives sodium ethanoate (CH₃COONa) and water.

CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

Thus, compound C is Ethanoic acid.

Q7. Look at Figure 4.1 and answer the following questions

(a ) What change would you observe in the calcium hydroxide solution taken in tube B?

(b ) Write the reaction involved in test tubes A and B.

(c ) Would you expect the same change if ethanol is given instead of ethanoic acid?

(d ) How can a solution of lime water be prepared in the laboratory?

Answer:

(a ) Calcium hydroxide solution in test tube B will become milky due to the formation of calcium carbonate.

(b ) Reaction in test tube A:

CH₃​COOH + NaHCO₃ ​→ CH₃​COONa + CO₂ + H₂​O

Reaction in test tube B:

Ca(OH)₂ + CO₂ ​→ CaCO₃ ​+ H₂​O

(c ) If ethanol is given instead of ethanoic acid, similar changes won’t be observed because ethanol does not react with sodium hydrogen carbonate.

(d ) First, take distilled water in a beaker and mix calcium carbonate powder. After stirring entirely, wait till the mixture settles down. Decant the clear liquid from the beaker. This liquid is lime water.

Q8. How would you bring about the following conversions? Name the process and write the

reaction.

(a) Ethanol to Ethene.

(b) Propanol to Propanoic acid.

Answer:

(a) Ethanol is heated at 443 K in the presence of an excess of conc. Sulphuric acid. This reaction is known as dehydrogenation.

CH_3​CH₂​OH + Conc. H₂​SO₄ → ​CH₂ ​= CH₂ ​+ H₂​O.

(b) Propanol is treated with alkaline potassium permanganate or acidified potassium dichromate to get propanoic acid.

CH_3​CH₂​​CH₂​OH + Alkaline KMnO₄ ​/ Acidified K₂​Cr₂​O₇ ​​→ CH_3​CH₂​COOH

Q9. Draw the possible isomers of the compound with the molecular formula C₃H₆O and give their electron dot structures.

Answer:

The two possible isomers of the compound with the molecular formula C₂H₆O are

 

Electron dot structures of the compound with the molecular formula C₂H₆O are

Q10. Explain the given reactions with the examples

(a) Hydrogenation reaction

(b) Oxidation reaction

(c) Substitution reaction

(d) Saponification reaction

(e) Combustion reaction

Answer:

(a) Addition of hydrogen to an unsaturated hydrocarbon to get a saturated hydrocarbon is known as a hydrogenation reaction.

CH₂ ​= CH₂ ​+ H₂ + ​Ni → ​CH_3​ − ​CH_3​

(b) When oxygen is added to alcohol to make carboxylic acid, it is known as an oxidation reaction.

CH_3​CH₂​​CH₂​OH + Alkaline KMnO₄ ​/ Acidified K₂​Cr₂​O₇ ​​→ CH_3​CH₂​COOH

(c ) A substitution reaction is a class of chemical reactions in which another atom or group substitute an atom or group of atoms.

CH₄ + Cl₂ + Sunlight → CH₃Cl + HCl

(d) Saponification is a methodology of manufacturing soap by the hydrolysis of fats or oils with a base like sodium hydroxide.

Reaction: CH₃​COOC₂​H₅ + NaOH → CH₃​COONa + C₂​H₅​OH

(e) A combustion reaction is a chemical reaction in which a compound and an oxidant react to form heat and a new product.

Example: Burning of wood.

Q11. An organic compound A on heating with concentrated H₂SO₄ forms a compound B which on the addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of CO₂ and 3 moles of H₂O. Identify the compounds A, B and C and write the chemical equations of the reactions involved.

Answer:

Compound A is ethanol (CH_3​CH₂​OH). When it is heated with concentrated sulphuric acid, we get ethene (CH₂ ​= CH₂). Thus, compound B is ethene (CH₂ ​= CH₂).

CH_3​CH₂​OH + Conc.H₂​SO₄ ​​→ CH₂ ​= CH₂ ​+ H₂​O

When ethene (CH₂ ​= CH₂) is heated in the presence of nickel, we get ethane (CH₃ ​- CH₃).

Thus, compound C is ethane (CH₃ ​- CH₃).

CH₂ ​= CH₂ ​+ ​Ni​ ​​→ CH₃ ​- CH₃

When 1 mole of ethane (CH₃ ​- CH₃) is burnt, we get 2 moles of carbon dioxide (CO₂) and 3 moles of water (H₂O).

2 CH₃ ​- CH₃ + 7 O₂ ​→ 4 CO₂ ​+ 6 H₂​O

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