Properties of Homologous Series Class 10

In this article, we will learn about the properties of homologous series belonging to carbon and its compounds.

But first, we must know what is a homologous series?

You will find the following topics

   1.   What is a homologous series?

   2.   Properties of homologous series

   3. Examples of homologous series

   4.   Questions on homologous series

   5.   Quiz on homologous series

 

What is a homologous series?

The series of organic compounds or carbon compounds having similar functional groups and similar chemical properties is called a homologous series.

 

Properties of homologous series

   1.   All members of a homologous series can be prepared by the same method.

   2.   The members of a homologous series have the same functional group.

   3.   There is a difference of 1 carbon and 2 hydrogen atoms.

   4.   The molecular formula of any two successive members of a homologous series differs by a `-CH_2` unit.

      Example

       `CH_4` and  `C_2H_6` differ by `-CH_2`

   5.   The molecular masses of any two adjacent members of a homologous series differ by 14u.

      Example

    Molecular mass of `CH_4`= 12×1+4×1=16u

    Molecular mass of `C_2H_6` = 12×2+6×1=30u

    Difference = 30-16=14u

   6.   All the members of a homologous series show similar chemical properties.

   7.   Physical properties of members of a homologous series are graded with an increase in molecular mass.

   8.   All the members of a homologous series can be represented by a general formula.

      Example

       Alkane – `C_nH_(2n+2)`

       Alkene  - `C_nH_(2n)`

       Alkanol - `C_nH_(2n+1)OH`

   9.   Generally, the first member of a homologous series shows different behaviour from the rest of the members.

    Important homologous series on the basis of functional groups (General formula of  homolgous series)

Example  of homologous series

 

Homologous series of alkanes

Name	Chemical formula
Methane	`CH4`
Ethane	`C2H6`
Propane	`C3H8`
Butane	`C4H10`

 

Homologous series of alkenes

Name	Chemical formula
Ethene	`C2H4`
Propene	`C3H6`
Butene	`C4H8`
Pentene	`C5H10`

 

Homologous  series of alkynes

Name	Chemical formula
Ethyne	`C2H2`
Propyne	`C3H4`
Butyne	`C4H6`
Pentyne	`C5H8`

 

Homologous series of alcohols

Name	Chemical formula
Methanol	`CH3OH`
Ethanol	`C2H5OH`
Propanol	`C3H7OH`
Butanol	`C4H9OH`

 

Homologous  series of aldehydes

Name	Chemical formula
Methanal	`HCHO`
Ethanal	`CH3CHO`
Propenal	`C2H5CHO`
Butanal	`C3H7CHO`

 

Homologous series of carboxylic acids

Name	Chemical formula
Methanoic acid	`HCOOH`
Ethanoic acid	`CH3COOH`
Propanoic acid	`C2H5COOH`
Butanoic acid	`C3H7COOH`

 

Homologous series of ketone

Name	Chemical formula
Propanone	`CH3COCH3`
Butanone	`CH3CH2COCH3`
Pentanone	`CH3CH2COCH2CH3`
Hexanone	`CH3CH2CH2COCH2CH3`

 

                                      Quiz 

   More Topics 

1. Electron dot structure examples

    FAQs

   1.  What is the general formula for the homologous series that includes ethene?

Ans -  `C_nH_(2n)`

   2.  To what homologous series does butane belong?

Ans – Butane belongs to alkanes

 

   3.  What is the difference in the molecular formula of any two successive members of a homologous series?

Ans -  Two successive members of a  homologous series by -`CH_2`.

   4.  What is the difference between molecular masses of two adjacent members of a homologous series?

Ans – The molecular masses of two adjacent members of a homologous series differ by 14u.

   5.  Why do all members of a homologous series show similar chemical properties?

Ans – Because all members of a homologous series have similar functional groups.