Distinguishing Test for Organic Compounds
Since this sounds like an assignment, I am not going to give it all away. 

Does you have to use qualitative chemical tests? I don't even teach those anymore. They were supplanted by spectroscopic techniques in most professional labs decades ago.

IR spectroscopy would answer both questions quickly. 


Benzamide would have peaks characterizing an aromatic ring, for example:  $\ce{C}_{sp^2}\ce{-H}$ stretches around $3050-3100\ \mathrm{cm^{-1}}$. Ethanamide will not have these peaks, but will instead have $\ce{C}_{sp^3}\ce{-H}$ peaks $2800-3000\ \mathrm{cm^{-1}}$. There are other differences as well.
There are differences in the position (and sometimes number!) of carbonyl peaks between an anhydride and an acid halide. What are they?


So would mass spectrometry. Benzamide and ethanamide have different molar masses and different fragmentation patterns. Ethanoyl chloride... chlorine has two major isotopes. How can that help? 

NMR spectroscopy would also be useful. However, IR is cheap, fast, and easy.