Methane in pure form can be obtained by using

Chemical formula of methane is $\mathrm{C}{\mathrm{H}}_4.$The chemical name of soda lime is sodium hydroxide. When it is heated, it leads to a decarboxylation reaction in which carbon dioxide is removed from the compound.
The chemical reaction for the soda lime decarboxylation is given as follows:
$C{H}_{3}COONa+NaOH\to C{H}_4+N{a}_{2}C{O}_3$