A. HCl
Cl2 is known as Deacon process. This process is used during the manufacture of alkali's by Leblanc process.
B. Ethene
CH3CHO,
the above process, is known as Wacker process, which refers to the oxidation of ethene to acetaldehye in the presence of
PbCl2.
C. Alcohol
| FeSO4 |
| ─────▸ |
| H2O2 |
Aldehyde
Fenton reagent is a solution of
H2O2 with
FeSO4 and is used as catalyst to oxidise alcohols to aldehyde.
D. Alkyne
| Ni |
| ─────▸ |
| Complex |
Benzene, it is the reaction used to convert alkyne into benzene. In this reaction,
Ni is used as catalyst along with carbon monoxide (CO), which is used for carboxylation. The reaction is known as Reppe synthesis.
∴ Hence,
(a) is the correct option.