Q. 223.7( 3 Votes )

What are hydrocarbons? Write the name and general formula of (i) saturated hydro � carbons, (ii) unsaturated hydrocarbons, and draw the structure of one hydrocarbon of each type. How can an unsaturated hydrocarbon be made saturated?


What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions.

Answer :

Hydrocarbons are defined as the compounds which are composed of Hydrogen and Carbon atoms.

(i) The names and general formula for saturated Hydrocarbons is Alkane and the formula is: CnH2n+2 . The ‘n’ represents number of carbon atoms in molecule of the alkane.

(ii) The names and general formula for unsaturated hydrocarbons are: Alkene and Alkyne. The general formula for alkene is: CnH2n and for Alkyne, it is : CnH2n-2

Structure of saturated hydrocarbon:

Molecular formula for 1 carbon atom = CH4



Structure of unsaturated hydrocarbon:

Molecular formula for 2 carbon atom is Ethene C2H4

The structure of Ethene is as follows:


Molecular formula for 2 carbon atom is Ethyne C2H2

Unsaturated hydrocarbon can be made a saturated hydrocarbon by addition reaction. On addition of Hydrogen in presence of Nickle as catalyst, to a unsaturated hydrocarbon, results in formation of a saturated hydrocarbon. The chemical reaction is as follows:

This reaction is called Hydrogenation.


Chemically, detergents are sodium salts of a long chain benzene sulphonic acids.

The merits of using detergents for cleansing are as follows:

1. They are strong cleansing agents and

2. They are also able to form lather in both hard as well as soft water.

Demerits of using Detergents for cleansing are:

1. These are non-biodegradable substances and can’t be broken into simpler substances by microorganisms. They remain as such in the environment.

2. They creates pollution in environment and also harmful when eaten by any animal.

The reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions because they can form foam with both hard water as well as soft water.

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