The volume of dihydrogen required for complete hydrogenation of $0.5 \ dm^{3}$ of ethene at $\text{S.T.P.}$ is (in $dm^{3}$)

An organic compound $(A)$ on ozonolysis followed by treatment with zinc dust and water gives product $(P)$,which can be used to preserve biological specimens. Identify $(A)$.

What is the number of structural isomers possible for alkene with molecular formula $C_5H_{10}$?

$CH_3-CH_2-CH_2-Br$ $\xrightarrow{\text{alk. KOH}} A$ $\xrightarrow[(ii) H_2O_2/OH^{-}]{(i) BD_3/THF} B$; $B$ is:

$CH_3-C(CH_3)=CH-CH_3 \xrightarrow{Hg(OAc)_2/EtOH} (A) (90\%)$. The product $(A)$ of the above reaction is:

Which of the following reagents reacts with $but-1-ene$ to give an optically inactive product?