Acetylene can be prepared from

The reaction of acetylene with acetic acid in the presence of $Hg^{2+}$ at room temperature yields ....

Propyne on cyclic polymerisation gives

Which gas is used in metal welding?

The reagent for the reaction $R-CH_2-CCl_2-R \xrightarrow{\text{reagent}} R-C \equiv C-R$ is:

Give the main product of the following reactions:
$(i)$ $1,1,2,2-$tetrabromopropane + zinc powder in methanol.
$(ii)$ Reaction occurring on passing hydrogen gas through carbon electrodes at high temperature in an electric arc.