Ethylene is converted to $X$ on passing through a mixture of an acidified aqueous solution of palladium chloride and cupric chloride. Which of the following reagents readily take part in addition reaction with $X$?

One mole of an organic compound requires $0.5$ mole of oxygen to produce an acid. The compound may be

Number of molecules from the following which cannot give the iodoform reaction is $:$ Ethanol,Isopropyl alcohol,Bromoacetone,$2-$Butanol,$2-$Butanone,Butanal,$2-$Pentanone,$3-$Pentanone,Pentanal,and $3-$Pentanol.

Two aliphatic aldehydes $P$ and $Q$ react in the presence of aqueous $K_2CO_3$ to give compound $R$,which upon treatment with $HCN$ provides compound $S$. On acidification and heating,$S$ gives the product shown below:
$1.$ The compounds $P$ and $Q$ respectively are:
$2.$ The compound $R$ is:
$3.$ The compound $S$ is:
Give the answer for questions $1$,$2$ and $3$.

Which of the following is the correct statement for the given reaction?
$CH_3-CH=O + C_6H_5-CH=O \xrightarrow[\Delta]{OH^{\ominus}(aq)} X_{(C_4H_6O)} + Y_{(C_9H_8O)}$

Which reagent is used to distinguish between acetaldehyde and acetophenone?