Which of the following would be produced when acetylene reacts with $HCl$?

Identify the structures of $P$ and $Q$ in the following reaction sequence:

The trend in acidic behaviour of the following hydrocarbons is:
$a: HC \equiv CH$
$b: CH_2 = CH_2$
$c: CH_3 - CH_3$
$d: CH_3 - C \equiv CH$

The synthesis of $3-$octyne is achieved by adding a bromoalkane into a mixture of sodium amide and an alkyne. The bromoalkane and alkyne respectively are

Ethylidene dichloride can be prepared by the reaction of $HCl$ and

When calcium carbide is added to water,the gas that is evolved is