In the reaction,$CH_3-C \equiv C-CH_3 \xrightarrow{(i) X, (ii) Zn/H_2O} CH_3-C(=O)-C(=O)-CH_3$,$X$ is:

Acetylene reacts with $HCN$ in the presence of $Ba(CN)_2$ to yield

Which of the following reactions will yield $2, 2-$dibromopropane?

Which of the following will produce a chiral molecule after treatment with $H_2$/Lindlar's catalyst?

$(A)$ $\xrightarrow[dil. H_2SO_4]{HgSO_4} (B)$ $\xrightarrow{LiAlH_4} \underset{\text{racemic mixture}}{(C)}$
$\therefore$ reactant $(A)$ is

Ethylidene dichloride is obtained by the reaction of excess of $HCl$ with