Number of possible alkynes with formula $C_{5}H_{8}$ is

Which product is obtained from the reaction of calcium carbide with water?

In the following series of chemical reactions,identify $Z$.
$C_3H_7OH$ $\xrightarrow[160-180\,^{\circ}C]{Conc. H_2SO_4} X$ $\xrightarrow{Br_2} Y$ $\xrightarrow{Excess \ of \ Alc. KOH} Z$

$CH_3-C \equiv CH \xrightarrow[dil. H_2SO_4]{HgSO_4} (A)$
$CH_3-C \equiv CH \xrightarrow[(1) BH_3.THF]{(2) H_2O_2/HO^{-}} (B)$
Products $(A)$ and $(B)$ can be differentiated by:

Which of the following is weakly acidic?

$Ph-CH=CH-Ph$ $\xrightarrow[CCl_4]{Cl_2} X$ $\xrightarrow{2NaNH_2} Y$ $\xrightarrow[BaSO_4]{H_2+Pd} Z$. Product $Z$ is