Question

what is soda lime in preparation of methane

Answer 1

sodalime is sodium(NaOH) and CaO

Answer 2

 In the laboratory, methane is prepared by heating a mixture of sodium acetate and soda lime. Soda lime is a mixture of sodium hydroxide and calcium oxide.
A mixture of sodium acetate and soda lime is taken in the hard glass test tube and heated with a Bunsen flame. Methane gas evolved is collected by the downward displacement of water.