How is:

(a) methane and

(b) ethane prepared in the laboratory?

(a) Laboratory preparation of methane

A mixture of sodium ethanoate (sodium acetate) and soda lime is taken in a hard glass test tube and heated over a bunsen flame.

$\underset{\text{ sodium acetate}}{\text{CH}$3\text{COONa}} + \underset{\text{sodalime}}{\text{NaOH}} \xrightarrow[300\degree\text{C}]{\text{CaO}} \underset{\text{methane}}{\text{C}\text{H}4}↑ + \text{Na}2\text{CO}3

The gas evolved is collected by downward displacement of water since it is slightly soluble in water and is lighter than air.

(b) Laboratory preparation of ethane

A mixture of sodium propionate and soda lime is taken in a boiling tube and heated over a bunsen flame.

$\underset{\text{sodium propionate}}{\text{C}$2\text{H}5\text{COONa}} + \underset{\text{sodalime}}{\text{NaOH}} \xrightarrow[300\degree\text{C}]{\text{CaO}} \underset{\text{ethane}}{\text{C}2\text{H}6} ↑ + \text{Na}2\text{CO}3

The gas evolved is collected by downward displacement of water.