Can you help in this question ?

Here P2O5 acts like a dehydrating agent and Y should be a compound formed after removal of water from starting material ...Y is an amide CH3CONH2 (acetamide).Now we are adding water in amide (acidified hydrolysis of amide) it will give us carboxylic acid.
8)Remember all acid derivatives give carboxylic acids on acid catalyzed or base catalyzed hydrolysis. 

So Z should be  acetic acid (CH3COOH)

Thanks Uma mam - Its a good point to remember that all acid derivatives hydrolyzed to give carboxylic  acids.

P2O5 is a good dehydrating agent. Can you give me some more example of dehydrating agent in organic chemistry.

Conc H2SO4 also acts as dehydrating agent in many reactions.