Question

Explain briefly about methane.

Explain in your own words.

Answer 1

$\underline{\boxed{\sf{Methane}}}$

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎It is a simple memeber of saturated hydrocarbons with the molecular formula $\sf{{CH}_{4}}$.

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎H

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎|

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎H — ‎ ‎‎ ‎C ‎ ‎‎— H

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎|

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎H

${\underline{\underline{\bf{Occurence:}}}}$

Natural gas contains mainly methane. Natural gas is formed by the anaerobic decomposition of organic matter by bacteria present inside the earth's crust. It is also found in marshy places. Hence, it is commonly known as marsh gas. In coal mines, methane which causes explosions and fire, accumulates.

${\underline{\underline{\bf{Physical\: properties:}}}}$

• It is a colourless and odourless gas.
• It is insoluble in water.
• It is lighter than air.
• It causes global warming as it is a greenhouse gas.

${\underline{\underline{\bf{Chemical\: properties:}}}}$

1) Methane on combustion burns with a blue flame giving out carbon dioxide and water.

• $\sf{{CH}_{4}+{2O}_{2}\longrightarrow {CO}_{2}+{2H}_{2}O+Energy}$

2) It reacts with chlorine gas in the presence of sunlight, by displacing one, two, three or all of its hydrogen atoms:

• $\sf{{CH}_{4}+{Cl}_{2}\xrightarrow{\sf{Sunlight}}{CH}_{3}Cl+HCl}$
• $\sf{{CH}_{3}Cl+{Cl}_{2}\xrightarrow{\sf{Sunlight}}{CH}_{2}{Cl}_{2}+HCl}$
• $\sf{{CH}_{2}{Cl}_{2}+{Cl}_{2}\xrightarrow{\sf{Sunlight}}{CHCl}_{3}+HCl}$
• $\sf{{CHCl}_{3}+{Cl}_{2}\xrightarrow{\sf{Sunlight}}{CCl}_{4}+HCl}$

3) Methane on heating in the absence of air decomposes into carbon and hydrogen. The carbon so obtained is called carbon black. This reaction is called pyrolysis (cracking).

• $\sf{{CH}_{4}\longrightarrow C+{2H}_{2}}$

${\underline{\underline{\bf{Preparation\:of\: methane:}}}}$

On heating anhydrous sodium acetate with soda lime, methane is formed along with sodium carbonate.

• $\sf{{CH}_{3}COONa+NaOH\overset{\Delta}{\longrightarrow}{CH}_{4}{Na}_{2}{CO}_{3}}$

Methane gas produced during the reaction is collected over water by the downward displacement of water since it is lighter than air and insoluble in water.

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Answer 2

Answer:

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