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:

The number of $\pi$-bonds in the product formed by passing acetylene through dilute sulphuric acid containing mercuric sulphate is

Propene and propyne can be distinguished by

Which of the following compounds on hydration (addition of $H_2O$) with $H_2SO_4/HgSO_4/H_2O$ gives an aldehyde as the major product?

What is the product obtained upon hydrogenation of the following compound in the presence of a poisoned palladium catalyst?

$C_2H_2$ $\xrightarrow{\text{dil. } H_2SO_4, HgSO_4} A$ $\xrightarrow{[O]} B$ $\xrightarrow{NaOH} C$ $\xrightarrow{NaOH/CaO} D$
$[D]$ is -