Acetylene reacts with a $42\% H_2SO_4$ solution containing $1\% HgSO_4$ to give

Reactant $P$ (an alkyne) gives products $Q$ (trans-alkene) or $R$ (cis-alkene).
The possible reagents are:
$(I) \ 2Na/liq. NH_3$
$(II) \ H_2/Pd/CaCO_3$ (quinoline)
$(III) \ 2H_2/Pd/C$
Which of the following statements is/are correct with respect to the above conversion?

The product$(s)$ obtained via oxymercuration $(HgSO_4 + H_2SO_4)$ of $but-1-yne$ would be

Consider the following sequence,where $A$ can be:
$A$ $(C_{3}H_{6}Cl_{2})$ $\xrightarrow[2. \, H^{+} \, (mild)]{1. \, \text{alcoholic } KOH / \Delta, \text{ followed by } NaNH_{2} / \Delta}$ $B$ $\xrightarrow[H_{2}O_{2} / OH^{-}]{B_{2}H_{6}}$ $C$
$A$ $\xrightarrow{aq. \, KOH \, (excess)}$ $C$
Identify $A$.

Which of the following gases,when passed through a warm dilute solution of $H_2SO_4$ in the presence of $HgSO_4$,gives acetaldehyde?

Which of the following does not react with acetylene?