Name: Physical Properties of Alkanes
Uploaded: 2019-07-19
Duration: 4 min 41 s
Description: Alkanes are organic compounds that consist of single-bonded carbon and hydrogen atoms. Let’s watch the video and learn some of the important physical propert...

Question

How methane can be prepared? What are the chief properties of these compounds? Explain the statement "Methane is a saturated hydrocarbon."

Accepted Answer

Aluminium carbide undergoes hydrolysis to produce methane and aluminium hydroxide. This reaction is a simple method of obtaining methane in the laboratory.

$\underset{Aluminium carbide}{{Al}_{4} C_{3}} + \underset{Water}{12 H_{2} O} \to \underset{Aluminium hydroxide}{4 Al {(OH)}_{3}} + \underset{Methane}{3 {CH}_{4}}$

Methane is a saturated hydrocarbon known as alkanes. Chief properties of these compounds are:
(A) Physical properties

(a) The first four alkanes are colourless gases with a petrol like smell, the next thirteen ( $C_{5} - C_{17}$ ) are colourless liquids and higher alkanes ( $C_{18}$ onward) are colourless solids.

(b) Alkanes being non-polar in nature are insoluble in water, whereas they dissolve in non-polar solvents like benzene, carbon tetrachloride etc. Their solubility decreases with the increase in their molecular mass.

(c) Boiling points: The boiling point rises regularly as the number of carbon atom in the alkane increases. But branched-chain isomers have lower boiling points than straight-chain isomers, which is due to a decrease in their surface area.

(B) Chemical properties

Alkanes mainly undergo two types of reactions :

(a) Substitution reactions: In the substitution reactions of alkanes, the direct replacement of one or more hydrogen atoms by halogen atoms or other monovalent groups takes place. It includes halogenation, nitration, and sulphonation.

(b) Thermal and catalytic reactions: The thermal decomposition of alkanes to produce lower hydrocarbons (saturated or unsaturated) is known as pyrolysis or cracking. When alkanes are heated at high temperatures in the absence of air, cracking occurs.

A saturated hydrocarbon is a hydrocarbon that contains no rings and contains only single bonds between the different atoms. Hence, ''Methane is a saturated hydrocarbon''.

How methane can be prepared? What are the chief properties of these compounds? Explain the statement "Methane is a saturated hydrocarbon."

Important Questions on Aliphatic Hydrocarbons : Saturated Hydrocarbons-Alkanes

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