Why are certain compounds called hydrocarbons? Write the general formula for homologous series of alkanes, alkenes and alkynes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkanes and also write a chemical equation to show the necessary conditions for the reaction to occur.



Hydrocarbons are the compounds containing carbon and hydrogen.

General Formula and Structure of first member of Homologous series

Homologous Series

General Formula

Structure of first member


C 2 H 2n+2

Structure of Methane


C n H 2n

Structure of Ethene


C n H 2n-2

Structure of Ethyne

Structure of Methane - Teachoo.png

Structure of Ethene - Teachoo.png

Structure of Ethyne - Teachoo.png

Addition reactions are those which convert alkenes to alkanes.

In this reaction, atoms are added over the double bond of an alkene thereby converting it to alkane.

Reaction equation:  

Conversion of Alkene to Alkane - Teachoo.png

The necessary conditions for the addition reaction to occur is

  • high temperature
  •  and presence of a catalyst such as nickel or palladium.
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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo