Identify the missing product in the following reaction:
$CH_3CH_2OH \xrightarrow[443 \ K]{H_2SO_4} (?)$

An alkene $(X)$ on ozonolysis followed by reduction gives the following products: $H-CHO$ ($2$ moles), $H-CO-CHO$, and $CH_3-CO-CO-CH_3$. The alkene $(X)$ is:

How many moles of $BH_3$ are needed to react completely with $2 \ mol$ of $1$-pentene in a hydroboration-oxidation reaction?

The major products $P$ and $Q$ from the below reactions are :
$CH_3CH=CH_2 \xrightarrow{HBr} P$
$CH_3CH=CH_2 \xrightarrow[(BH_3)_2]{H_2O, H_2O_2 / OH^-} Q$

Propene on hydroboration and oxidation produces

In methyl alcohol solution,bromine reacts with ethylene to yield $BrCH_2CH_2OCH_3$ in addition to $1, 2-dibromoethane$ because: