Dear Aspirant,

I explaining the whole process here,

• To Nitrobenzene, on addition of H2/Pd and Ethanol , it will change to Aniline.
• To this Aniline, NaNo2+HCl at 273-278K is added, changing it to Benzenediazonium Chloride.
• To this Benzenediazonium Chloride, CuCN/KCN is added, changing it to Benzonitrile.
• Hydrolysis i.e addition of H3O+ is added to this Benzonitrile, finally changing it to Benzoic Acid.

I hope this helps you!