Which of the following gases is used for welding?

$CH_3-CH_2-CH(Cl)_2$ $\xrightarrow[{[Excess]}]{{NaNH_2}} P$ $\xrightarrow{{CH_3Cl}} Q$,$Q$ will be

Which reaction converts $2$-hexyne into $trans$-$2$-hexene?

Predict the product $C$ obtained in the following reaction of $1-$butyne: $CH_3-CH_2-C \equiv CH + HCl$ $\rightarrow B$ $\xrightarrow{HI} C$

Propyne reacts with excess $HBr$ to form the compound $Z$. The structure of $Z$ is:

$A \xrightarrow{Ag_2O} \text{ppt}$
$A$ $\xrightarrow{Hg^{2+} / H^{+}} B$ $\xrightarrow{NaBH_4} C$ $\xrightarrow{conc. HCl / ZnCl_2} \text{Turbidity within 5 minutes}$.
Consider the following reactions,'$A$' is: