Class 10th Science Chapter 4 – Carbon and Its Compounds | Functional Groups

Carbon and Its Compounds | Functional Groups

Class 10 Science | Chapter 4 | CBSE + Foundation + Competitive Level

Functional Groups | क्रियात्मक समूह

1. What is a Functional Group? | क्रियात्मक समूह क्या है?

English:
A functional group is an atom or group of atoms present in an organic compound that determines its characteristic chemical properties and reactions.

Hindi:
कार्बनिक यौगिक में उपस्थित वह परमाणु या परमाणुओं का समूह जो उसके विशिष्ट रासायनिक गुणों और अभिक्रियाओं को निर्धारित करता है, क्रियात्मक समूह (Functional Group) कहलाता है।

Examples:

–OH → Alcohol
–CHO → Aldehyde
>C=O → Ketone
–COOH → Carboxylic Acid
–X → Halo group

2. Importance of Functional Groups | क्रियात्मक समूह का महत्व

Functional groups are important because they:

• Determine characteristic chemical reactions.
• Determine many chemical properties of organic compounds.
• Help classify organic compounds.
• Help in systematic nomenclature.
• Allow compounds with the same functional group to show similar types of reactions.

Hindi:

• यौगिक की विशिष्ट रासायनिक अभिक्रियाएँ निर्धारित करते हैं।
• रासायनिक गुणों को प्रभावित करते हैं।
• कार्बनिक यौगिकों का वर्गीकरण करने में सहायता करते हैं।
• IUPAC नामकरण में सहायता करते हैं।
• समान functional group वाले यौगिकों में समान प्रकार की अभिक्रियाएँ देखी जा सकती हैं।

3. Important Functional Groups | महत्वपूर्ण क्रियात्मक समूह

Functional Group	Symbol	Class of Compound	Suffix	Example
Alcohol	–OH	Alcohol	-ol	Ethanol
Aldehyde	–CHO	Aldehyde	-al	Ethanal
Ketone	>C=O	Ketone	-one	Propanone
Carboxylic Acid	–COOH	Carboxylic acid	-oic acid	Ethanoic acid
Halo Group	–X	Haloalkane	fluoro-, chloro-, bromo-, iodo-	Chloroethane

4. Alcohol Functional Group –OH | अल्कोहॉल समूह

The functional group of alcohols is:

–OH

The –OH group is called the hydroxyl group when it acts as the characteristic group of an alcohol.

Example:

CH₃–CH₂–OH

Ethanol

Hindi:
Alcohol में –OH functional group उपस्थित होता है। इसका IUPAC suffix सामान्यतः -ol होता है।

5. Aldehyde Functional Group –CHO | एल्डिहाइड समूह

Aldehydes contain the functional group:

–CHO

The carbon of the aldehyde group is attached to at least one hydrogen atom and is at the end of the carbon chain.

Example:

CH₃–CHO

Ethanal

Suffix: -al

Example: Ethane → Ethanal

6. Ketone Functional Group >C=O | कीटोन समूह

Ketones contain a carbonyl group:

>C=O

In a ketone, the carbonyl carbon is bonded to two carbon-containing groups.

Example:

CH₃–CO–CH₃

Propanone

Suffix: -one

7. Carboxylic Acid Functional Group –COOH | कार्बोक्सिलिक अम्ल

Carboxylic acids contain:

–COOH

The –COOH group contains both a carbonyl group (C=O) and a hydroxyl group (–OH).

Example:

CH₃–COOH

Ethanoic acid

Suffix: -oic acid

8. Halo Functional Group | हैलो समूह

Halogens can replace hydrogen atoms in hydrocarbons. The common halogens are:

• Fluorine → F
• Chlorine → Cl
• Bromine → Br
• Iodine → I

The general representation is:

–X

where X represents a halogen atom.

Examples:

CH₃Cl → Chloromethane

CH₃CH₂Cl → Chloroethane

9. Carbonyl Group | कार्बोनिल समूह

The group:

C=O

is called the carbonyl group.

It is present in several important organic compounds, including aldehydes and ketones.

Compound	Carbonyl Position
Aldehyde	At the end of the chain
Ketone	Within the carbon chain

10. Aldehyde vs Ketone | एल्डिहाइड और कीटोन में अंतर

Property	Aldehyde	Ketone
Functional group	–CHO	>C=O
Position	End of carbon chain	Inside carbon chain
Suffix	-al	-one
Example	Ethanal	Propanone

11. Alcohol vs Carboxylic Acid | अल्कोहॉल और कार्बोक्सिलिक अम्ल

Property	Alcohol	Carboxylic Acid
Functional group	–OH	–COOH
Suffix	-ol	-oic acid
Example	Ethanol	Ethanoic acid
Acidic nature	Generally not acidic like carboxylic acids	Acidic

12. Same Carbon Chain, Different Functional Groups

A carbon chain can carry different functional groups, producing compounds with different chemical properties.

Example: CH₃CH₂OH → Ethanol
CH₃CHO → Ethanal
CH₃COOH → Ethanoic acid

Although these compounds contain two carbon atoms, their functional groups are different, so their properties and reactions are different.

13. Functional Groups and Homologous Series

Members of a homologous series have:

• The same functional group.
• The same general formula.
• Similar chemical properties.
• Successive members differing by –CH₂–.

Example: Alcohol series

CH₃OH → Methanol
C₂H₅OH → Ethanol
C₃H₇OH → Propanol
C₄H₉OH → Butanol

14. How to Identify Functional Groups? | Functional Group की पहचान

Observed Group	Functional Group	Compound Type
–OH	Hydroxyl	Alcohol
–CHO	Aldehyde	Aldehyde
>C=O	Carbonyl	Ketone
–COOH	Carboxyl	Carboxylic acid
–Cl	Chloro	Halo compound
–Br	Bromo	Halo compound

15. Functional Groups in IUPAC Nomenclature

Functional groups influence the suffix or prefix used in the name of an organic compound.

Functional Group	IUPAC Naming	Example
–OH	-ol	Ethanol
–CHO	-al	Ethanal
>C=O	-one	Propanone
–COOH	-oic acid	Ethanoic acid
–Cl	chloro-	Chloroethane
–Br	bromo-	Bromoethane

16. Easy Memory Trick | याद रखने की आसान ट्रिक

OH → OL
Alcohol → -ol

CHO → AL
Aldehyde → -al

CO → ONE
Ketone → -one

COOH → OIC ACID
Carboxylic acid → -oic acid

17. 30 MCQs | बहुविकल्पीय प्रश्न

Q1. What is a functional group?

A. A group that determines characteristic properties

B. Only a carbon atom

C. Only a hydrogen atom

D. A mixture of compounds

Answer: A

Q2. Which functional group is present in alcohols?

A. –COOH

B. –CHO

C. –OH

D. –CO–

Answer: C

Q3. The functional group –CHO represents:

A. Alcohol

B. Aldehyde

C. Ketone

D. Acid

Answer: B

Q4. Which functional group is characteristic of ketones?

A. –OH

B. –COOH

C. –CHO

D. >C=O

Answer: D

Q5. The functional group –COOH belongs to:

A. Alcohols

B. Aldehydes

C. Carboxylic acids

D. Ketones

Answer: C

Q6. The suffix used for alcohols is:

A. -ol

B. -al

C. -one

D. -oic acid

Answer: A

Q7. The suffix used for aldehydes is:

A. -ol

B. -al

C. -one

D. -yne

Answer: B

Q8. The suffix used for ketones is:

A. -al

B. -ol

C. -one

D. -ane

Answer: C

Q9. The suffix used for carboxylic acids is:

A. -one

B. -ol

C. -al

D. -oic acid

Answer: D

Q10. Which compound contains –OH?

A. Ethanol

B. Ethanal

C. Propanone

D. Ethanoic acid

Answer: A

Q11. CH₃CHO contains:

A. –OH

B. –COOH

C. –CHO

D. –Cl

Answer: C

Q12. CH₃COCH₃ is an example of:

A. Alcohol

B. Ketone

C. Aldehyde

D. Alkane

Answer: B

Q13. CH₃COOH contains:

A. –COOH

B. –OH only

C. –CHO

D. –Cl

Answer: A

Q14. Which group is called the carbonyl group?

A. –OH

B. –COOH

C. C=O

D. –CHO

Answer: C

Q15. In an aldehyde, the carbonyl group is generally:

A. At the end of the carbon chain

B. Always in the middle

C. Absent

D. Attached to three carbons

Answer: A

Q16. In a simple ketone, the carbonyl carbon is attached to:

A. Hydrogen only

B. Two carbon-containing groups

C. No carbon

D. One oxygen only

Answer: B

Q17. Ethanol belongs to which class?

A. Aldehyde

B. Ketone

C. Alcohol

D. Acid

Answer: C

Q18. Ethanal belongs to:

A. Aldehyde

B. Alcohol

C. Ketone

D. Alkane

Answer: A

Q19. Propanone belongs to:

A. Alcohol

B. Aldehyde

C. Ketone

D. Acid

Answer: C

Q20. Ethanoic acid contains:

A. –COOH

B. –CHO

C. –OH only

D. –CO–

Answer: A

Q21. Which functional group contains both C=O and –OH?

A. Aldehyde

B. Carboxyl

C. Ketone

D. Alkene

Answer: B

Q22. Which is the functional group of halo compounds?

A. –X

B. –OH

C. –COOH

D. –CHO

Answer: A

Q23. Which one is a halogen?

A. O

B. N

C. Cl

D. C

Answer: C

Q24. CH₃Cl is named:

A. Chloromethane

B. Methanol

C. Methanal

D. Methanoic acid

Answer: A

Q25. Which pair has the same functional group?

A. Ethanol and propanol

B. Ethanol and ethanal

C. Ethanal and ethanoic acid

D. Propanone and ethanol

Answer: A

Q26. Members of the same homologous series generally have:

A. Different functional groups

B. Same functional group

C. No carbon atoms

D. Different general formulas

Answer: B

Q27. Which functional group determines that a compound is an alcohol?

A. –COOH

B. –CHO

C. –OH

D. C=C

Answer: C

Q28. Which compound has the suffix "-one"?

A. Ethanol

B. Ethanal

C. Ethanoic acid

D. Propanone

Answer: D

Q29. Which functional group is represented by –COOH?

A. Hydroxyl

B. Carboxyl

C. Carbonyl only

D. Halo

Answer: B

Q30. Why are functional groups important in organic chemistry?

A. They determine characteristic chemical behaviour

B. They only increase mass

C. They remove all carbon atoms

D. They prevent all reactions

Answer: A

18. 30 Subjective Questions | वर्णनात्मक प्रश्न

1 Mark
Q1. What is a functional group?

Answer: An atom or group of atoms responsible for the characteristic chemical properties of an organic compound is called a functional group.

1 Mark
Q2. Write the functional group of alcohols.

Answer: –OH

1 Mark
Q3. Write the functional group of aldehydes.

Answer: –CHO

1 Mark
Q4. Write the functional group of carboxylic acids.

Answer: –COOH

1 Mark
Q5. Write the functional group of ketones.

Answer: >C=O

2 Marks
Q6. What is the importance of functional groups?

Answer: Functional groups determine the characteristic chemical properties and reactions of organic compounds and help classify them.

2 Marks
Q7. Write the functional groups present in ethanol and ethanoic acid.

Answer:
Ethanol → –OH
Ethanoic acid → –COOH

2 Marks
Q8. Differentiate between aldehyde and ketone.

Answer:
Aldehyde → –CHO, generally at the end of the chain.
Ketone → >C=O, with carbonyl carbon bonded to two carbon-containing groups.

2 Marks
Q9. What is a carbonyl group?

Answer: The group C=O is called the carbonyl group.

2 Marks
Q10. Name the functional groups in CH₃CHO and CH₃COOH.

Answer:
CH₃CHO → Aldehyde group
CH₃COOH → Carboxyl group

3 Marks
Q11. Explain the functional group –OH.

Solution:
The –OH group is the characteristic functional group of alcohols. It is called the hydroxyl group. Alcohols containing this group generally have the suffix -ol in IUPAC nomenclature. Example: CH₃CH₂OH is ethanol.

3 Marks
Q12. Explain the functional group –COOH.

Solution:
–COOH is the carboxyl group. It is characteristic of carboxylic acids. It contains both C=O and –OH. Its IUPAC suffix is generally -oic acid. Example: CH₃COOH is ethanoic acid.

3 Marks
Q13. What are halo compounds?

Answer: Organic compounds in which one or more hydrogen atoms of a hydrocarbon are replaced by halogen atoms such as F, Cl, Br or I are called halo compounds.

3 Marks
Q14. Give three examples of functional groups with their compounds.

Answer:
–OH → Ethanol
–CHO → Ethanal
–COOH → Ethanoic acid

3 Marks
Q15. How does a functional group affect an organic compound?

Answer: A functional group gives an organic compound its characteristic chemical behaviour and influences its reactions and many physical properties.

4 Marks
Q16. Explain alcohol, aldehyde, ketone and carboxylic acid functional groups.

Class	Functional Group	Example
Alcohol	–OH	Ethanol
Aldehyde	–CHO	Ethanal
Ketone	>C=O	Propanone
Carboxylic acid	–COOH	Ethanoic acid

4 Marks
Q17. Differentiate between aldehyde and ketone.

Solution:

Aldehyde	Ketone
Contains –CHO	Contains >C=O
Carbonyl group generally at the end	Carbonyl group within the carbon chain
Suffix -al	Suffix -one
Example: Ethanal	Example: Propanone

4 Marks
Q18. Explain the relationship between functional groups and IUPAC nomenclature.

Solution:
Functional groups help determine the suffix or prefix used in IUPAC naming.

–OH → -ol
–CHO → -al
>C=O → -one
–COOH → -oic acid

Thus, identifying the functional group is an important step in naming an organic compound.

4 Marks
Q19. Write the functional groups and IUPAC names of the following:
(a) CH₃CH₂OH
(b) CH₃CHO
(c) CH₃COCH₃
(d) CH₃COOH

Answer:
(a) –OH → Ethanol
(b) –CHO → Ethanal
(c) >C=O → Propanone
(d) –COOH → Ethanoic acid

4 Marks
Q20. Explain the carbonyl group and name two classes of compounds containing it.

Solution:
The C=O group is called the carbonyl group. It is present in:

1. Aldehydes → –CHO
2. Ketones → >C=O

Examples: Ethanal → CH₃CHO
Propanone → CH₃COCH₃

5 Marks
Q21. Describe the major functional groups studied in Class 10 carbon compounds.

Solution: The important functional groups are:

1. –OH: Alcohol
2. –CHO: Aldehyde
3. >C=O: Ketone
4. –COOH: Carboxylic acid
5. –X: Halo group, where X may be F, Cl, Br or I

These groups determine characteristic chemical behaviour and are important in classification and nomenclature.

5 Marks
Q22. Explain how functional groups help in classifying carbon compounds.

Answer:
Organic compounds can be classified according to the functional group they contain. For example, compounds containing –OH are alcohols, those containing –CHO are aldehydes, compounds with >C=O are ketones, and compounds containing –COOH are carboxylic acids. This classification makes the study of a large number of carbon compounds easier.

5 Marks
Q23. Compare alcohols, aldehydes, ketones and carboxylic acids.

Class	Group	Suffix	Example
Alcohol	–OH	-ol	Ethanol
Aldehyde	–CHO	-al	Ethanal
Ketone	>C=O	-one	Propanone
Carboxylic acid	–COOH	-oic acid	Ethanoic acid

5 Marks
Q24. Explain why two compounds having the same number of carbon atoms can have different properties.

Solution:
Two compounds may have the same number of carbon atoms but different functional groups. Since the functional group determines characteristic chemical behaviour, the compounds can have different chemical properties and reactions.

Example: CH₃CH₂OH → Ethanol
CH₃CHO → Ethanal
CH₃COOH → Ethanoic acid

All contain two carbon atoms but belong to different functional classes.

5 Marks
Q25. Explain the relation between functional groups and homologous series.

Answer:
Members of a homologous series have the same functional group and similar chemical properties. Successive members differ by –CH₂–. For example, methanol, ethanol, propanol and butanol form a homologous series of alcohols because all contain the –OH functional group.

6 Marks
Q26. Explain all important functional groups of Class 10 Carbon and Its Compounds with examples.

Solution:

1. Alcohol –OH: Example: CH₃CH₂OH → Ethanol
2. Aldehyde –CHO: Example: CH₃CHO → Ethanal
3. Ketone >C=O: Example: CH₃COCH₃ → Propanone
4. Carboxylic acid –COOH: Example: CH₃COOH → Ethanoic acid
5. Halo group –X: Example: CH₃Cl → Chloromethane

These functional groups help determine classification, nomenclature and characteristic reactions.

6 Marks
Q27. A compound has the formula CH₃CH₂OH. Identify its functional group, class and IUPAC name.

Solution: Formula = CH₃CH₂OH

Functional group = –OH
Class = Alcohol
Number of carbon atoms = 2
Root = eth-
Suffix = -ol

IUPAC name = Ethanol

6 Marks
Q28. Identify the functional group and IUPAC name of:
(a) CH₃CHO
(b) CH₃COCH₃
(c) CH₃COOH

Solution:
(a) CH₃CHO
Functional group = –CHO
Class = Aldehyde
Name = Ethanal

(b) CH₃COCH₃
Functional group = >C=O
Class = Ketone
Name = Propanone

(c) CH₃COOH
Functional group = –COOH
Class = Carboxylic acid
Name = Ethanoic acid

6 Marks
Q29. Explain the difference between –OH, –CHO, >C=O and –COOH functional groups.

Solution:

Group	Class	Suffix	Example
–OH	Alcohol	-ol	Ethanol
–CHO	Aldehyde	-al	Ethanal
>C=O	Ketone	-one	Propanone
–COOH	Carboxylic acid	-oic acid	Ethanoic acid

6 Marks
Q30. Why are functional groups considered important in the study of carbon compounds?

Solution: Functional groups are important because:

1. They determine characteristic chemical properties.
2. They determine characteristic chemical reactions.
3. They help classify organic compounds.
4. They are important for IUPAC nomenclature.
5. They help identify the chemical nature of a compound.
6. Compounds with the same functional group often show related chemical behaviour.

19. Quick Revision | त्वरित पुनरावृत्ति

⭐ Most Important Functional Groups:

–OH → Alcohol → -ol

–CHO → Aldehyde → -al

>C=O → Ketone → -one

–COOH → Carboxylic Acid → -oic acid

–X → Halo Group → fluoro/chloro/bromo/iodo

20. Exam Booster | परीक्षा के लिए महत्वपूर्ण

Must Remember:

CH₃CH₂OH → Ethanol → –OH
CH₃CHO → Ethanal → –CHO
CH₃COCH₃ → Propanone → >C=O
CH₃COOH → Ethanoic acid → –COOH
CH₃Cl → Chloromethane → –Cl

21. One-Line Revision | एक लाइन में पूरा Topic

Functional Group → Class of Compound → Characteristic Properties → IUPAC Suffix/Prefix

क्रियात्मक समूह → यौगिक का वर्ग → विशिष्ट गुण → IUPAC नामकरण

Class 10th Science Chapter 4 – Carbon and Its Compounds | Nomenclature of Carbon Compounds

Carbon and Its Compounds | Nomenclature of Carbon Compounds

Class 10 Science | Chapter 4 | CBSE + Foundation + Competitive Level

Nomenclature of Carbon Compounds | कार्बन यौगिकों का नामकरण

1. What is Nomenclature? | नामकरण क्या है?

English:
The systematic naming of organic compounds according to rules laid down by the International Union of Pure and Applied Chemistry (IUPAC) is called IUPAC nomenclature.

Hindi:
कार्बनिक यौगिकों को IUPAC द्वारा निर्धारित नियमों के अनुसार व्यवस्थित रूप से नाम देना नामकरण (Nomenclature) कहलाता है।

Example:

CH₄ → Methane
C₂H₆ → Ethane
C₃H₈ → Propane
C₄H₁₀ → Butane

2. Why is Nomenclature Necessary? | नामकरण की आवश्यकता

Organic compounds are extremely numerous. A systematic naming system helps us:

• Identify a compound uniquely.
• Understand its carbon skeleton.
• Know the functional group.
• Determine the position of a functional group or multiple bond.
• Communicate chemical information internationally.

Hindi:

• यौगिक की पहचान आसानी से होती है।
• Carbon chain की जानकारी मिलती है।
• Functional group की पहचान होती है।
• Functional group या multiple bond की स्थिति ज्ञात होती है।
• पूरी दुनिया में एक समान नाम का उपयोग किया जा सकता है।

3. Carbon Chain Root Words | कार्बन श्रृंखला के मूल शब्द

Number of Carbon Atoms	Root Word	Example
1	Meth-	Methane
2	Eth-	Ethane
3	Prop-	Propane
4	But-	Butane
5	Pent-	Pentane
6	Hex-	Hexane
7	Hept-	Heptane
8	Oct-	Octane
9	Non-	Nonane
10	Dec-	Decane

Easy Trick:
1 Meth – 2 Eth – 3 Prop – 4 But – 5 Pent – 6 Hex – 7 Hept – 8 Oct – 9 Non – 10 Dec

4. Suffixes in Carbon Compounds | प्रत्यय

Type of Compound	Bond / Functional Group	Suffix	Example
Alkane	C–C	-ane	Ethane
Alkene	C=C	-ene	Ethene
Alkyne	C≡C	-yne	Ethyne
Alcohol	–OH	-ol	Ethanol
Aldehyde	–CHO	-al	Ethanal
Ketone	>C=O	-one	Propanone
Carboxylic Acid	–COOH	-oic acid	Ethanoic acid

5. Naming of Alkanes | एल्केन का नामकरण

Alkanes contain only single bonds. General formula:

CₙH₂ₙ₊₂

Examples:

Formula	Name
CH₄	Methane
C₂H₆	Ethane
C₃H₈	Propane
C₄H₁₀	Butane
C₅H₁₂	Pentane
C₆H₁₄	Hexane

6. Naming of Alkenes | एल्कीन का नामकरण

Alkenes contain at least one carbon-carbon double bond. The suffix -ene is used.

Formula	Name
C₂H₄	Ethene
C₃H₆	Propene
C₄H₈	Butene
C₅H₁₀	Pentene

7. Naming of Alkynes | एल्काइन का नामकरण

Alkynes contain at least one carbon-carbon triple bond. The suffix -yne is used.

Formula	Name
C₂H₂	Ethyne
C₃H₄	Propyne
C₄H₆	Butyne
C₅H₈	Pentyne

8. Functional Groups and Their Names | क्रियात्मक समूह

Functional Group	Name	Suffix	Example
–OH	Alcohol	-ol	Ethanol
–CHO	Aldehyde	-al	Ethanal
>C=O	Ketone	-one	Propanone
–COOH	Carboxylic acid	-oic acid	Ethanoic acid

9. Basic Steps of IUPAC Nomenclature | नामकरण के मुख्य चरण

Step 1: Find the longest continuous carbon chain.

Step 2: Identify the principal functional group or multiple bond.

Step 3: Number the carbon chain from the appropriate end.

Step 4: Identify substituents such as methyl or ethyl.

Step 5: Assign locants (position numbers).

Step 6: Write the name using the correct prefix, root and suffix.

10. Longest Carbon Chain Rule | सबसे लंबी श्रृंखला

The parent chain is generally the longest continuous carbon chain containing the principal functional group and, where applicable, the maximum number of multiple bonds.

Example:

CH₃–CH₂–CH₂–CH₃

There are four carbon atoms. Therefore: But + ane = Butane

11. Numbering of Carbon Chain | कार्बन श्रृंखला की संख्या

The carbon chain is numbered from the end that gives the important feature the lowest possible locant. For a simple functional-group example:

CH₃–CH₂–CH₂–OH

Numbering starts from the –OH end:

HO–CH₂–CH₂–CH₃

Propan-1-ol

Important: Numbering is not always simply from the nearest substituent. The principal functional group and multiple bonds receive appropriate priority under the nomenclature rules.

12. Prefixes for Alkyl Groups | एल्किल समूह

Alkyl Group	Formula	Name
–CH₃	CH₃–	Methyl
–C₂H₅	C₂H₅–	Ethyl
–C₃H₇	C₃H₇–	Propyl
–C₄H₉	C₄H₉–	Butyl

13. Naming Branched-Chain Compounds | शाखित श्रृंखला का नामकरण

Consider:

CH₃–CH(CH₃)–CH₃

The longest chain contains three carbon atoms: Propane There is a methyl group attached to carbon number 2. Therefore the name is:

2-Methylpropane

Consider:

CH₃–CH(CH₃)–CH₂–CH₃

Longest chain = 4 carbons → Butane
Methyl group = carbon 2

Name:

2-Methylbutane

14. More Than One Substituent | एक से अधिक प्रतिस्थापी

If identical substituents occur more than once, prefixes are used:

• 2 → di
• 3 → tri
• 4 → tetra

Example: 2,2-Dimethylpropane

Here two methyl groups are present.

15. Position of Double Bond | द्विबंध की स्थिति

For alkenes, the position of the double bond is indicated by a number. Example: CH₂=CH–CH₂–CH₃

There are four carbon atoms → but-
Double bond starts at carbon 1.

Name:

But-1-ene

Another example: CH₃–CH=CH–CH₃

Double bond begins at carbon 2.

Name:

But-2-ene

16. Position of Triple Bond | त्रिबंध की स्थिति

Example: CH≡C–CH₂–CH₃

Four carbon atoms → but-
Triple bond begins at carbon 1.

Name:

But-1-yne

17. Naming Alcohols | अल्कोहॉल का नामकरण

Alcohols contain the functional group: –OH The suffix -ol is used.

Example: CH₃–CH₂–OH

2 carbon atoms → eth-
Alcohol → -ol

Name: Ethanol

Example: CH₃–CH₂–CH₂–OH

Three carbon atoms → prop-
–OH at carbon 1.

Name: Propan-1-ol

18. Naming Aldehydes | एल्डिहाइड का नामकरण

Aldehyde functional group: –CHO Suffix: -al

Example: CH₃–CHO

Two carbon atoms → eth-
Aldehyde → -al

Name = Ethanal

19. Naming Ketones | कीटोन का नामकरण

Ketone functional group: >C=O Suffix: -one

Example: CH₃–CO–CH₃

Three carbon atoms → prop-
Ketone → -one

Name = Propanone

20. Naming Carboxylic Acids | कार्बोक्सिलिक अम्ल

Carboxylic acid functional group: –COOH Suffix: -oic acid

Example: CH₃–COOH

Two carbon atoms → eth-
Acid → -oic acid

Name = Ethanoic acid

21. General Naming Pattern | सामान्य नामकरण प्रारूप

Prefix + Parent/Root + Suffix

For example:
2-Methylpropane

2 → position
Methyl → substituent
Prop → 3 carbon parent chain
ane → single bonds

22. Important IUPAC Examples

Structure / Formula	IUPAC Name
CH₄	Methane
CH₃–CH₃	Ethane
CH₃–CH₂–CH₃	Propane
CH₃–CH₂–CH₂–CH₃	Butane
CH₂=CH₂	Ethene
CH₂=CH–CH₃	Propene
CH≡CH	Ethyne
CH₃–CH₂–OH	Ethanol
CH₃–CHO	Ethanal
CH₃–CO–CH₃	Propanone
CH₃–COOH	Ethanoic acid
CH₃–CH(CH₃)–CH₃	2-Methylpropane

23. 30 MCQs | बहुविकल्पीय प्रश्न

Q1. The systematic naming of organic compounds is called:

A. Isomerism

B. Nomenclature

C. Catenation

D. Polymerisation

Answer: B

Q2. Which organisation is associated with systematic chemical nomenclature?

A. WHO

B. UNESCO

C. IUPAC

D. UNICEF

Answer: C

Q3. The root word for one carbon atom is:

A. Meth

B. Eth

C. Prop

D. But

Answer: A

Q4. The root word for four carbon atoms is:

A. Prop

B. Pent

C. But

D. Hex

Answer: C

Q5. The suffix used for alkanes is:

A. -ene

B. -yne

C. -ol

D. -ane

Answer: D

Q6. The suffix -ene indicates:

A. Double bond

B. Triple bond

C. Alcohol

D. Carboxylic acid

Answer: A

Q7. The suffix -yne indicates:

A. Single bond

B. Double bond

C. Triple bond

D. –OH group

Answer: C

Q8. What is the IUPAC name of CH₄?

A. Ethane

B. Methane

C. Propane

D. Butane

Answer: B

Q9. What is the IUPAC name of C₂H₆?

A. Methane

B. Propane

C. Ethane

D. Ethene

Answer: C

Q10. The IUPAC name of CH₂=CH₂ is:

A. Ethane

B. Ethyne

C. Ethanol

D. Ethene

Answer: D

Q11. The IUPAC name of CH≡CH is:

A. Ethyne

B. Ethene

C. Ethane

D. Methyne

Answer: A

Q12. The functional group of alcohol is:

A. –COOH

B. –CHO

C. –OH

D. –CO–

Answer: C

Q13. CH₃CH₂OH is:

A. Methanol

B. Ethanol

C. Propanol

D. Ethanal

Answer: B

Q14. The suffix used for alcohols is:

A. -ol

B. -al

C. -one

D. -oic acid

Answer: A

Q15. CH₃CHO is named:

A. Ethanol

B. Ethanoic acid

C. Ethanal

D. Ethanone

Answer: C

Q16. The suffix for aldehydes is:

A. -one

B. -ol

C. -al

D. -yne

Answer: C

Q17. CH₃COCH₃ is:

A. Propanone

B. Propanol

C. Propanal

D. Propanoic acid

Answer: A

Q18. The functional group of carboxylic acids is:

A. –OH

B. –CHO

C. –COOH

D. –O–

Answer: C

Q19. The IUPAC name of CH₃COOH is:

A. Methanoic acid

B. Ethanoic acid

C. Propanoic acid

D. Ethanol

Answer: B

Q20. The alkyl group –CH₃ is called:

A. Ethyl

B. Propyl

C. Methyl

D. Butyl

Answer: C

Q21. The alkyl group –C₂H₅ is called:

A. Methyl

B. Ethyl

C. Propyl

D. Butyl

Answer: B

Q22. What is the IUPAC name of CH₃CH(CH₃)CH₃?

A. Butane

B. 1-Methylpropane

C. 2-Methylpropane

D. Pentane

Answer: C

Q23. In 2-methylpropane, the parent chain contains:

A. 2 carbon atoms

B. 3 carbon atoms

C. 4 carbon atoms

D. 5 carbon atoms

Answer: B

Q24. What does the prefix "di-" indicate?

A. One substituent

B. Two identical substituents

C. Three substituents

D. Four substituents

Answer: B

Q25. What is the IUPAC name of CH₂=CHCH₂CH₃?

A. Butane

B. But-2-ene

C. But-1-ene

D. Propene

Answer: C

Q26. What is the IUPAC name of CH₃CH=CHCH₃?

A. But-1-ene

B. But-2-ene

C. Butane

D. Butyne

Answer: B

Q27. Which is the correct IUPAC name of CH₃CH₂CH₂OH?

A. Propanol

B. Propan-1-ol

C. Propan-2-ol

D. Ethanol

Answer: B

Q28. Which rule is important when selecting a parent chain?

A. Select the shortest chain only

B. Select any random chain

C. Select an appropriate longest continuous chain

D. Select only a branched chain

Answer: C

Q29. What is the IUPAC name of CH₃CH₂CH₃?

A. Methane

B. Ethane

C. Propane

D. Butane

Answer: C

Q30. In "2-methylbutane", the number 2 represents:

A. Number of carbon atoms

B. Position of methyl group

C. Number of hydrogen atoms

D. Molecular mass

Answer: B

24. 30 Subjective Questions | वर्णनात्मक प्रश्न

1 Mark
Q1. What is nomenclature?
नामकरण क्या है?

Answer: The systematic naming of chemical compounds according to prescribed rules is called nomenclature.

1 Mark
Q2. What does IUPAC stand for?

Answer: International Union of Pure and Applied Chemistry.

1 Mark
Q3. Write the root word for three carbon atoms.

Answer: Prop-

1 Mark
Q4. Write the suffix used for alkenes.

Answer: -ene

1 Mark
Q5. Name the functional group –OH.

Answer: Hydroxyl group / Alcohol functional group.

2 Marks
Q6. Write the IUPAC names of CH₄ and C₂H₆.

Answer: CH₄ = Methane; C₂H₆ = Ethane.

2 Marks
Q7. Write the IUPAC names of C₂H₄ and C₂H₂.

Answer: C₂H₄ = Ethene; C₂H₂ = Ethyne.

2 Marks
Q8. Write two rules of IUPAC nomenclature.

Answer:

1. Select an appropriate longest parent carbon chain.
2. Number the chain according to the lowest appropriate locant rule.

2 Marks
Q9. Name the following compounds:
(a) CH₃CH₂OH
(b) CH₃COOH

Answer:
(a) Ethanol
(b) Ethanoic acid

2 Marks
Q10. What are methyl and ethyl groups?

Answer:
Methyl = –CH₃
Ethyl = –C₂H₅

3 Marks
Q11. Explain the importance of the longest carbon chain in nomenclature.

Solution:
The longest appropriate continuous carbon chain is selected as the parent chain. Its carbon count determines the root name such as meth-, eth-, prop-, but-, etc. Substituents and functional groups are then identified in relation to this parent chain.

3 Marks
Q12. Name the following compounds:
(a) CH₃CH₂CH₃
(b) CH₃CH₂CH₂CH₃
(c) CH₃CH₂CH₂CH₂CH₃

Answer:
(a) Propane
(b) Butane
(c) Pentane

3 Marks
Q13. Explain the meaning of root word and suffix in nomenclature.

Answer:
Root word: Indicates the number of carbon atoms in the parent chain.
Suffix: Indicates the type of bonding or principal functional group.

3 Marks
Q14. Name the following:
(a) CH₂=CH₂
(b) CH₂=CHCH₃
(c) CH≡CH

Answer:
(a) Ethene
(b) Propene
(c) Ethyne

3 Marks
Q15. What is a substituent? Give two examples.

Answer:
A group attached to the parent carbon chain in place of a hydrogen atom is called a substituent. Examples:
–CH₃ = methyl
–C₂H₅ = ethyl

4 Marks
Q16. Explain the basic steps involved in IUPAC nomenclature.

Solution:

1. Select the appropriate parent carbon chain.
2. Identify the principal functional group or multiple bond.
3. Number the parent chain appropriately.
4. Identify substituents and their positions.
5. Use the correct root and suffix.
6. Combine all parts to obtain the systematic name.

4 Marks
Q17. Explain the nomenclature of 2-methylpropane.

Solution: Structure:

CH₃–CH(CH₃)–CH₃

Longest continuous chain = 3 carbon atoms → Propane.
Substituent = methyl.
Methyl group is attached to carbon 2.

Name = 2-Methylpropane.

4 Marks
Q18. Explain the difference between -ane, -ene and -yne.

Suffix	Bond	Example
-ane	Single	Ethane
-ene	Double	Ethene
-yne	Triple	Ethyne

4 Marks
Q19. Give the IUPAC names of:
(a) CH₃CH₂OH
(b) CH₃CHO
(c) CH₃COCH₃
(d) CH₃COOH

Answer:
(a) Ethanol
(b) Ethanal
(c) Propanone
(d) Ethanoic acid

4 Marks
Q20. Explain the naming of alkenes with suitable examples.

Solution:
Alkenes contain at least one C=C double bond. The parent chain is selected and the suffix -ene is used. The position of the double bond may be indicated by a locant. Examples:

CH₂=CH₂ → Ethene
CH₂=CHCH₂CH₃ → But-1-ene
CH₃CH=CHCH₃ → But-2-ene

5 Marks
Q21. Explain the IUPAC naming system for carbon compounds.

Solution:
IUPAC nomenclature gives systematic names to organic compounds. The main steps are:

1. Select an appropriate parent carbon chain.
2. Count carbon atoms and select the correct root word.
3. Identify the functional group or multiple bond.
4. Number the chain appropriately.
5. Identify substituents and their positions.
6. Use the appropriate suffix.

This gives a unique systematic name.

5 Marks
Q22. Explain root words from 1 to 10 carbon atoms.

Carbon	Root
1	Meth
2	Eth
3	Prop
4	But
5	Pent
6	Hex
7	Hept
8	Oct
9	Non
10	Dec

5 Marks
Q23. Explain the naming of alcohols, aldehydes, ketones and carboxylic acids.

Compound	Functional Group	Suffix	Example
Alcohol	–OH	-ol	Ethanol
Aldehyde	–CHO	-al	Ethanal
Ketone	>C=O	-one	Propanone
Carboxylic acid	–COOH	-oic acid	Ethanoic acid

5 Marks
Q24. Explain the nomenclature of branched-chain compounds with an example.

Solution: Example:

CH₃–CH(CH₃)–CH₂–CH₃

Longest chain = 4 carbon atoms → Butane.
Substituent = methyl.
Methyl group is located at carbon 2.

IUPAC name = 2-Methylbutane.

5 Marks
Q25. Explain the role of locants in IUPAC nomenclature.

Answer:
Locants are numbers used to indicate the position of substituents, functional groups or multiple bonds in a carbon chain. Examples:

But-1-ene → double bond at carbon 1.
But-2-ene → double bond at carbon 2.
2-Methylpropane → methyl group at carbon 2.

6 Marks
Q26. Explain the complete procedure for naming a branched carbon compound.

Solution: The procedure is:

1. Identify the longest appropriate parent chain.
2. Count the number of carbon atoms.
3. Choose the corresponding root word.
4. Number the chain from the appropriate end.
5. Identify every substituent.
6. Determine the position of each substituent.
7. Use di-, tri-, etc. if identical substituents occur more than once.
8. Combine the locants, substituent names, parent name and suffix.

Example: CH₃–CH(CH₃)–CH₂–CH₃

Longest chain = Butane
Substituent = Methyl
Position = 2

Name = 2-Methylbutane.

6 Marks
Q27. Give the IUPAC names of the following compounds:

(a) CH₃CH₂CH₂CH₃
(b) CH₃CH(CH₃)CH₃
(c) CH₂=CHCH₃
(d) CH₃CH=CHCH₃
(e) CH₃CH₂OH
(f) CH₃COOH

Answer:

(a) Butane
(b) 2-Methylpropane
(c) Propene
(d) But-2-ene
(e) Ethanol
(f) Ethanoic acid

6 Marks
Q28. Explain how the number of carbon atoms and type of bonding determine the name of a hydrocarbon.

Solution:
The number of carbon atoms determines the root word:
1 → meth, 2 → eth, 3 → prop, 4 → but, etc.

The type of carbon-carbon bonding determines the suffix:
Single bond → -ane
Double bond → -ene
Triple bond → -yne

Examples: CH₃CH₃ → Ethane
CH₂=CH₂ → Ethene
CH≡CH → Ethyne

6 Marks
Q29. A compound has the structure CH₃–CH(CH₃)–CH₂–CH₃. Determine its IUPAC name and explain each part of the name.

Solution: Longest continuous chain contains 4 carbon atoms.
Therefore root = But-

There is one methyl substituent.
Numbering from the nearer end gives methyl at carbon 2.

Single bonds → -ane

Therefore: 2-Methylbutane

2 = position of methyl group
Methyl = substituent
But = four-carbon parent chain
ane = single bonds

6 Marks
Q30. Explain why IUPAC nomenclature is important in the study of carbon compounds.

Answer: IUPAC nomenclature is important because:

1. It gives each compound a systematic name.
2. It avoids confusion caused by different common names.
3. It helps identify the carbon skeleton.
4. It indicates important functional groups and bonding features.
5. It helps communicate chemical information internationally.
6. It provides a systematic method for naming a very large number of organic compounds.

25. Quick Revision | त्वरित पुनरावृत्ति

⭐ IUPAC Naming Formula:

Position + Prefix + Root + Suffix

Root Words:
1 Meth | 2 Eth | 3 Prop | 4 But | 5 Pent | 6 Hex | 7 Hept | 8 Oct | 9 Non | 10 Dec

Important Suffixes:
Alkane → -ane
Alkene → -ene
Alkyne → -yne
Alcohol → -ol
Aldehyde → -al
Ketone → -one
Carboxylic acid → -oic acid

26. Exam Booster | परीक्षा के लिए महत्वपूर्ण

Remember these examples:

CH₄ → Methane
C₂H₆ → Ethane
C₃H₈ → Propane
C₄H₁₀ → Butane

CH₂=CH₂ → Ethene
CH₂=CHCH₃ → Propene

CH≡CH → Ethyne
CH₃CH₂OH → Ethanol
CH₃CHO → Ethanal
CH₃COCH₃ → Propanone
CH₃COOH → Ethanoic acid
CH₃CH(CH₃)CH₃ → 2-Methylpropane

27. One-Line Revision | एक लाइन में पूरा Chapter

Number of Carbon → Root Word → Bond/Functional Group → Suffix → Position/Prefix → IUPAC Name

कार्बन की संख्या → Root Word → Bond/Functional Group → Suffix → Position/Prefix → नाम

Class 10th Science Chapter 4 – Carbon and Its Compounds | Homologous Series

Carbon and Its Compounds | Homologous Series

Class 10 Science | Chapter 4 | CBSE + Foundation + Competitive Level

Carbon and Its Compounds | Homologous Series

1. What is a Homologous Series? | समजातीय श्रेणी क्या है?

English:
A homologous series is a group or family of organic compounds having:

• The same functional group.
• The same general formula.
• Similar chemical properties.
• A gradual change in physical properties.
• Successive members differing by a –CH₂– unit.

Hindi:
समजातीय श्रेणी (Homologous Series) कार्बनिक यौगिकों का ऐसा समूह है जिसमें:

• समान functional group होता है।
• समान general formula होता है।
• रासायनिक गुण लगभग समान होते हैं।
• भौतिक गुणों में क्रमिक परिवर्तन होता है।
• क्रमिक सदस्यों में –CH₂– का अंतर होता है।

2. Definition | परिभाषा

English:
A homologous series is a family of organic compounds with the same functional group and similar chemical properties, in which successive members differ by a –CH₂– group.

Hindi:
समजातीय श्रेणी समान functional group वाले कार्बनिक यौगिकों का समूह है, जिसमें क्रमिक सदस्यों के molecular formula में –CH₂– का अंतर होता है।

3. Difference of –CH₂– Between Successive Members

Consider the alkane series:

Compound	Formula	Carbon Atoms
Methane	CH₄	1
Ethane	C₂H₆	2
Propane	C₃H₈	3
Butane	C₄H₁₀	4
Pentane	C₅H₁₂	5

C₂H₆ − CH₄ = CH₂
C₃H₈ − C₂H₆ = CH₂
C₄H₁₀ − C₃H₈ = CH₂

Exam Point:
Successive members of a homologous series differ by one –CH₂– unit, whose relative molecular mass is 14 u.
Hindi: प्रत्येक अगले सदस्य में molecular mass सामान्यतः 14 u बढ़ता है।

4. General Formula of Homologous Series

Different homologous series have different general formulae.

Series	General Formula	Example
Alkanes	CₙH₂ₙ₊₂	CH₄, C₂H₆, C₃H₈
Alkenes	CₙH₂ₙ	C₂H₄, C₃H₆, C₄H₈
Alkynes	CₙH₂ₙ₋₂	C₂H₂, C₃H₄, C₄H₆
Alcohols	CₙH₂ₙ₊₁OH	CH₃OH, C₂H₅OH
Carboxylic Acids	CₙH₂ₙ₊₁COOH	HCOOH, CH₃COOH

5. Homologous Series of Alkanes | एल्केन की समजातीय श्रेणी

Name	Formula	Molecular Mass
Methane	CH₄	16 u
Ethane	C₂H₆	30 u
Propane	C₃H₈	44 u
Butane	C₄H₁₀	58 u
Pentane	C₅H₁₂	72 u
Hexane	C₆H₁₄	86 u

Alkanes → CₙH₂ₙ₊₂

6. Homologous Series of Alkenes | एल्कीन

Alkenes contain at least one C=C double bond. General formula:

CₙH₂ₙ

Compound	Formula
Ethene	C₂H₄
Propene	C₃H₆
Butene	C₄H₈
Pentene	C₅H₁₀

7. Homologous Series of Alkynes | एल्काइन

Alkynes contain at least one C≡C triple bond. General formula:

CₙH₂ₙ₋₂

Compound	Formula
Ethyne	C₂H₂
Propyne	C₃H₄
Butyne	C₄H₆
Pentyne	C₅H₈

8. Homologous Series of Alcohols | अल्कोहॉल

Alcohols contain the functional group –OH. General formula:

CₙH₂ₙ₊₁OH

Alcohol	Formula
Methanol	CH₃OH
Ethanol	C₂H₅OH
Propanol	C₃H₇OH
Butanol	C₄H₉OH

9. Homologous Series of Carboxylic Acids

Carboxylic acids contain the functional group: –COOH Examples:

Compound	Formula
Methanoic acid	HCOOH
Ethanoic acid	CH₃COOH
Propanoic acid	C₂H₅COOH
Butanoic acid	C₃H₇COOH

10. Characteristics of a Homologous Series

1. Same functional group
Members have the same functional group.

2. Same general formula
All members follow the same general formula.

3. Similar chemical properties
Because the functional group is the same, their chemical reactions are similar.

4. Difference of –CH₂–
Two consecutive members differ by –CH₂–.

5. Molecular mass increases by 14 u
Since CH₂ = 12 + 2 = 14 u.

6. Gradual change in physical properties
Boiling point, melting point, density and solubility may change gradually as molecular mass increases.

11. Why Do Members Have Similar Chemical Properties?

English:
The chemical properties of organic compounds mainly depend on their functional groups. Since all members of a homologous series contain the same functional group, they show similar chemical reactions.

Hindi:
कार्बनिक यौगिकों के रासायनिक गुण मुख्य रूप से उनके functional group पर निर्भर करते हैं। क्योंकि homologous series के सभी सदस्यों में functional group समान होता है, इसलिए उनके रासायनिक गुण समान होते हैं।

12. Variation in Physical Properties

As molecular size increases:

• Boiling point generally increases.
• Melting point generally changes gradually.
• Density generally increases gradually.
• Solubility and physical state may change.

Example: Methane → gas
Ethane → gas
Propane → gas
Butane → gas
Higher alkanes → liquids/solids depending on molecular size.

13. Why is the Difference 14 u?

CH₂ = 12 + (2 × 1)

CH₂ = 14 u

Therefore, when one carbon and two hydrogen atoms are added to the next member, molecular mass increases by 14 u.

14. Example: Finding the Next Member

Suppose the compound is: C₃H₈ The next member will contain one additional –CH₂– group.

C₃H₈ + CH₂ = C₄H₁₀

Therefore: Propane → Butane

Similarly:

C₄H₁₀ + CH₂ = C₅H₁₂

Butane → Pentane

15. Importance of Homologous Series

Homologous series helps us to:

1. Classify organic compounds.
2. Predict the formula of the next member.
3. Predict molecular mass.
4. Understand similarities in chemical reactions.
5. Study gradual changes in physical properties.
6. Understand organic chemistry systematically.

16. 30 MCQs | बहुविकल्पीय प्रश्न

Q1. What is the characteristic difference between two successive members of a homologous series?

A. –CH₃

B. –CH₂–

C. –OH

D. –COOH

Answer: B — Successive members differ by –CH₂–.

Q2. What is the relative molecular mass of –CH₂–?

A. 12 u

B. 13 u

C. 14 u

D. 15 u

Answer: C — 12 + 2(1) = 14 u.

Q3. Which of the following represents the general formula of alkanes?

A. CₙH₂ₙ₊₂

B. CₙH₂ₙ

C. CₙH₂ₙ₋₂

D. CₙHₙ

Answer: A

Q4. Which functional group is present in alcohols?

A. –COOH

B. –CHO

C. –OH

D. –CO–

Answer: C

Q5. Which pair belongs to the same homologous series?

A. CH₄ and C₂H₆

B. CH₄ and C₂H₄

C. C₂H₆ and C₂H₄

D. C₂H₂ and C₃H₈

Answer: A

Q6. What is the molecular formula of propane?

A. C₃H₆

B. C₃H₈

C. C₃H₄

D. C₂H₆

Answer: B

Q7. Which compound is the next homologous member after ethane?

A. Methane

B. Ethene

C. Propane

D. Butane

Answer: C

Q8. The general formula of alkenes is:

A. CₙH₂ₙ₊₂

B. CₙH₂ₙ

C. CₙH₂ₙ₋₂

D. CₙHₙ₊₂

Answer: B

Q9. Which bond is characteristic of alkenes?

A. C–C single bond only

B. C=C double bond

C. C≡C triple bond

D. C–H ionic bond

Answer: B

Q10. Which of the following is an alkyne?

A. C₂H₆

B. C₂H₄

C. C₂H₂

D. CH₄

Answer: C

Q11. The members of a homologous series have:

A. Different functional groups

B. Same functional group

C. Different general formulae

D. No chemical similarity

Answer: B

Q12. Which property changes gradually in a homologous series?

A. Chemical formula only

B. Atomic number

C. Physical properties

D. Functional group

Answer: C

Q13. Which is the molecular formula of butane?

A. C₄H₈

B. C₄H₁₀

C. C₄H₆

D. C₃H₈

Answer: B

Q14. Which compound follows the formula CₙH₂ₙ?

A. Alkane

B. Alkene

C. Alkyne

D. Alcohol

Answer: B

Q15. What is the molecular formula of pentane?

A. C₅H₁₀

B. C₅H₈

C. C₅H₁₂

D. C₄H₁₀

Answer: C

Q16. Which one is NOT a characteristic of a homologous series?

A. Same functional group

B. Same general formula

C. Successive members differ by CH₂

D. Completely different chemical properties

Answer: D

Q17. Methanol and ethanol belong to:

A. Alkane series

B. Alkene series

C. Alcohol homologous series

D. Alkyne series

Answer: C

Q18. Which functional group is found in carboxylic acids?

A. –OH

B. –COOH

C. –CHO

D. –O–

Answer: B

Q19. Which is the next member after C₃H₈?

A. C₄H₁₀

B. C₄H₈

C. C₃H₆

D. C₅H₁₂

Answer: A

Q20. Why do members of the same homologous series show similar chemical properties?

A. Same colour

B. Same molecular mass

C. Same functional group

D. Same number of atoms

Answer: C

Q21. What is the molecular mass of ethane?

A. 16 u

B. 28 u

C. 30 u

D. 44 u

Answer: C

Q22. Which of the following is a member of alkane homologous series?

A. C₃H₆

B. C₄H₁₀

C. C₂H₂

D. C₅H₁₀

Answer: B

Q23. What is the general formula of alkynes?

A. CₙH₂ₙ₊₂

B. CₙH₂ₙ

C. CₙH₂ₙ₋₂

D. CₙHₙ

Answer: C

Q24. Which compound has the formula C₄H₈?

A. Butane

B. Butene

C. Butyne

D. Propane

Answer: B

Q25. The boiling point generally increases with:

A. Decreasing molecular size

B. Increasing molecular size

C. Decreasing carbon atoms

D. Removal of functional group

Answer: B

Q26. Which pair differs by –CH₂–?

A. CH₄ and C₂H₆

B. CH₄ and C₂H₄

C. C₂H₆ and C₃H₆

D. C₂H₄ and C₃H₄

Answer: A

Q27. Which statement is correct?

A. Homologous members have different functional groups.

B. Successive members differ by CH₂.

C. They have completely different chemical properties.

D. Their general formula is always different.

Answer: B

Q28. Ethanoic acid belongs to which homologous series?

A. Alcohols

B. Alkenes

C. Carboxylic acids

D. Alkynes

Answer: C

Q29. If one member has molecular mass 44 u, the next member in the same series will generally have molecular mass:

A. 54 u

B. 58 u

C. 60 u

D. 72 u

Answer: B — 44 + 14 = 58 u.

Q30. Which factor mainly determines the chemical properties of a homologous series?

A. Functional group

B. Colour

C. Physical state

D. Molecular volume only

Answer: A

17. 30 Subjective Questions | वर्णनात्मक प्रश्न

1 Mark
Q1. What is a homologous series?
समजातीय श्रेणी क्या है?

Answer: A homologous series is a family of organic compounds having the same functional group and successive members differing by –CH₂–.
Hindi: समान functional group वाले कार्बनिक यौगिकों की श्रेणी जिसमें क्रमिक सदस्य –CH₂– से भिन्न हों।

1 Mark
Q2. What is the molecular mass of –CH₂–?

Answer: 14 u.

1 Mark
Q3. Name the functional group of alcohols.

Answer: Hydroxyl group, –OH.

1 Mark
Q4. Write the general formula of alkanes.

Answer: CₙH₂ₙ₊₂.

1 Mark
Q5. Give one example of a homologous pair.

Answer: Methane (CH₄) and ethane (C₂H₆).

2 Marks
Q6. State two characteristics of a homologous series.

Answer:

1. Members have the same functional group.
2. Successive members differ by –CH₂–.

2 Marks
Q7. Why do members of a homologous series have similar chemical properties?

Answer: Because members of a homologous series contain the same functional group, which determines their characteristic chemical reactions.

2 Marks
Q8. Why does molecular mass increase by 14 u in a homologous series?

Solution:
Each successive member contains one additional CH₂ group.

CH₂ = 12 + 2 = 14 u Therefore molecular mass increases by 14 u.

2 Marks
Q9. Write the first four members of the alkane series.

Answer:
Methane – CH₄
Ethane – C₂H₆
Propane – C₃H₈
Butane – C₄H₁₀

2 Marks
Q10. Write two differences between alkanes and alkenes.

Answer:

Alkanes	Alkenes
Only single C–C bonds	At least one C=C bond
CₙH₂ₙ₊₂	CₙH₂ₙ

3 Marks
Q11. Explain the term homologous series with an example.

Solution:
A homologous series is a family of organic compounds having the same functional group and general formula. Consecutive members differ by –CH₂–. Example: CH₄ → C₂H₆ → C₃H₈ → C₄H₁₀ Each successive member differs by CH₂.

3 Marks
Q12. Write three characteristics of a homologous series.

Answer:

1. Same functional group.
2. Same general formula.
3. Successive members differ by –CH₂–.

3 Marks
Q13. Write the first five members of the alkane homologous series.

Answer:
CH₄, C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂.

3 Marks
Q14. Explain the variation of physical properties in a homologous series.

Answer:
As molecular size increases, physical properties such as boiling point, melting point and density generally change gradually. The change occurs because molecular mass and intermolecular forces increase.

3 Marks
Q15. Find the next two members after C₂H₆ in the alkane series.

Solution:
C₂H₆ + CH₂ = C₃H₈
C₃H₈ + CH₂ = C₄H₁₀

Answer: C₃H₈ and C₄H₁₀.

4 Marks
Q16. Explain four important characteristics of a homologous series.

Answer:

1. Same functional group.
2. Same general formula.
3. Successive members differ by CH₂.
4. Members show similar chemical properties but gradual changes in physical properties.

4 Marks
Q17. Compare alkanes, alkenes and alkynes.

Series	Bond	General Formula	Example
Alkanes	Single	CₙH₂ₙ₊₂	C₂H₆
Alkenes	Double	CₙH₂ₙ	C₂H₄
Alkynes	Triple	CₙH₂ₙ₋₂	C₂H₂

4 Marks
Q18. Explain why chemical properties are similar but physical properties change gradually in a homologous series.

Solution:
Chemical properties depend mainly on the functional group, which remains the same. Hence chemical properties are similar. Physical properties depend considerably on molecular mass and size. Since molecular mass increases gradually by 14 u, physical properties also change gradually.

4 Marks
Q19. Write the first four members of alcohol homologous series.

Answer:
Methanol – CH₃OH
Ethanol – C₂H₅OH
Propanol – C₃H₇OH
Butanol – C₄H₉OH

4 Marks
Q20. Explain with examples that consecutive members of a homologous series differ by CH₂.

Solution:
CH₄ → C₂H₆ Difference = CH₂

C₂H₆ → C₃H₈ Difference = CH₂

C₃H₈ → C₄H₁₀ Difference = CH₂

Thus consecutive members differ by one CH₂ unit.

5 Marks
Q21. Explain homologous series in detail with an example.

Solution:
A homologous series is a family of organic compounds with the same functional group and general formula. Important characteristics:

1. Same functional group.
2. Same general formula.
3. Similar chemical properties.
4. Successive members differ by CH₂.
5. Molecular mass increases by 14 u.
6. Physical properties change gradually.

Example of alkanes: CH₄, C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂.

5 Marks
Q22. Explain the importance of homologous series in organic chemistry.

Answer:

1. Helps classify organic compounds.
2. Helps predict molecular formulae.
3. Helps predict the next member.
4. Helps understand similar chemical reactions.
5. Helps study changes in physical properties.

5 Marks
Q23. Describe the homologous series of alkanes with molecular formulae of the first six members.

Member	Formula
Methane	CH₄
Ethane	C₂H₆
Propane	C₃H₈
Butane	C₄H₁₀
Pentane	C₅H₁₂
Hexane	C₆H₁₄

All consecutive members differ by CH₂.

5 Marks
Q24. Explain the relationship between molecular mass and physical properties in a homologous series.

Solution:
The molecular size increases as CH₂ units are added. Consequently, intermolecular attractions generally increase. Therefore properties such as boiling point, melting point and density show a gradual trend with increasing molecular mass.

5 Marks
Q25. Differentiate between homologous series and isomers.

Homologous Series	Isomers
Same functional group and general formula.	Same molecular formula.
Successive members differ by CH₂.	Different structural arrangements.
Example: methane, ethane, propane.	Example: n-butane and isobutane.

6 Marks
Q26. Explain all major characteristics of a homologous series with suitable examples.

Solution: A homologous series has the following major characteristics:

1. Same functional group: Members contain the same functional group.
2. Same general formula: Members follow the same general formula.
3. Similar chemical properties: Same functional group produces similar chemical behaviour.
4. Difference of CH₂: Consecutive members differ by CH₂.
5. 14 u increase: Molecular mass increases by 14 u.
6. Gradual physical change: Boiling point, melting point and density change gradually.

Example: CH₄ → C₂H₆ → C₃H₈ → C₄H₁₀

6 Marks
Q27. Explain the homologous series of alkanes, alkenes and alkynes with their general formulae.

Series	General Formula	Examples
Alkanes	CₙH₂ₙ₊₂	CH₄, C₂H₆
Alkenes	CₙH₂ₙ	C₂H₄, C₃H₆
Alkynes	CₙH₂ₙ₋₂	C₂H₂, C₃H₄

All members within each series have similar chemical properties and consecutive members differ by CH₂.

6 Marks
Q28. How can you identify whether given compounds belong to the same homologous series?

Solution: Check the following:

1. Whether they have the same functional group.
2. Whether they follow the same general formula.
3. Whether their chemical properties are similar.
4. Whether successive members differ by CH₂.

Example: C₂H₆, C₃H₈ and C₄H₁₀ belong to the same alkane homologous series.

6 Marks
Q29. A compound has molecular formula C₄H₁₀. Find the next two members of its alkane homologous series and calculate their molecular masses.

Solution: C₄H₁₀ + CH₂ = C₅H₁₂
C₅H₁₂ + CH₂ = C₆H₁₄

Molecular mass of C₅H₁₂: 5 × 12 + 12 × 1 = 72 u

Molecular mass of C₆H₁₄: 6 × 12 + 14 × 1 = 86 u

Answer: C₅H₁₂ and C₆H₁₄; masses = 72 u and 86 u.

6 Marks
Q30. Explain why homologous series are useful for predicting properties of organic compounds.

Solution: A homologous series follows a definite pattern. Because consecutive members differ by CH₂ and have the same functional group:

• The molecular formula of the next member can be predicted.
• The molecular mass can be calculated.
• Similar chemical reactions can be predicted.
• Changes in physical properties can be estimated.

Therefore homologous series provides a systematic way to study large numbers of organic compounds.

18. Quick Revision | त्वरित पुनरावृत्ति

⭐ Homologous Series = Same Functional Group + Same General Formula + CH₂ Difference

Important Points:

• Successive members differ by –CH₂–.
• CH₂ has molecular mass 14 u.
• Chemical properties are similar.
• Physical properties change gradually.
• Alkanes → CₙH₂ₙ₊₂
• Alkenes → CₙH₂ₙ
• Alkynes → CₙH₂ₙ₋₂
• Alcohols contain –OH.
• Carboxylic acids contain –COOH.

19. Exam Booster | परीक्षा के लिए महत्वपूर्ण

Remember:

1. Homologous = Same functional group
2. Consecutive members = CH₂ difference
3. CH₂ = 14 u
4. Same series = Similar chemical properties
5. Increasing molecular mass = Gradual change in physical properties